LOW POWER TEST PATTERN GENERATION FOR

SYSTEM ON CHIP DEVICES

by

AFTAB FAROOQI, B.S.E.E., M.B.A.

A THESIS

IN

ELECTRICAL ENGINEERING

Submitted to the Graduate Faculty of Texas Tech University in

Partial Fulfillment of the Requirements for

the Degree of

MASTER OF SCIENCE

IN

ELECTRICAL ENGINEERING

Approved

Richard Gale Chairperson of the Committee

Tim Dallas

Accepted

John Borrelli Dean of the Graduate School

May, 2006

ACKNOWLEDGEMENTS

I would like to thank Dr. Gale, my mentor for the entire MSEE

Program, especially for his leadership in guiding me to define the scope of the thesis and helping me identify key milestones towards the completion of the project. Many thanks to Dr. Dallas for helping me break-down the overall thesis project to smaller manageable sub-projects. Thanks to Dr. Nutter for his assistance in helping me experiment the project using Xilinx. Dr. Karp always made herself available to help me decipher signal processing attributes included in the many IEEE papers I had to read for deeper understanding of the issues. Dr. Parten who was always there to help me breakdown complex issues included in the IEEE papers to simple algorithms for better conceptual understanding. Dr. Mitra for her guidance in helping me understand complex mathematical concepts behind signal processing algorithms.

I would like to honor Dr. Chris Monico of the mathematics department for helping me better understand random number generation theory especially the correlation between complex polynomials, matrices and LFSR’s. (Linear Feedback Shift Registers).

ii

Dr. Monico’s assistance was pivotal in helping me grasp the

fundamental mathematical concepts behind a very complex subject of low power pattern generation.

I would also like to thank Dr. Temkin’s candid and sincere steering to help me focus on the fundamental semiconductor manufacturing concepts for stronger technical foundation.

iii

TABLE OF CONTENTS ACKNOWLEDGEMENTS ii ABSTRACT vi LIST OF TABLES viii LIST OF FIGURES ix CHAPTER

I. INTRODUCTION 1

Project Motivation 1 Project Objectives 3 Thesis Outline 4

II. SOC BACKGROUND 6

SOC Attributes 6 SOC Design Tools and Methodology 7 SOC Power Consumption 10 SOC Manufacturing Processes 11 SOC Test and Assembly 13

III. SOC TEST 16

SOC Test Tools and Methodology 16 Test Approaches (External and Conventional

DFT) 18 Built-In-Self-Test (BIST) 19 BIST Pattern Generation Using LFSR 21

IV. LOW POWER PATTERN GENERATION 27

Idea Behind Low Power Test Pattern Generation 27

iv

A Technique to Produce Low Power Pattern 29 for BIST

Benchmark Design Circuits 34

V. RESULTS AND DISCUSSION

Simulation Using Standard LFSR Pattern 39 Simulation Using LP-LFSR 40 Power Consumption Using standard LFSR 41 Power Consumption Using LP-LFSR 43

Power Consumption Comparison 44 (Standard LFSR versus LP-LFSR) Summary and Conclusion 46 VI. RECOMMENDATIONS FOR FUTURE WORK 49

SELECTED BIBLIOGRAPHY 51 APPENDICES 54

A. PATTERN GENERATION CONTROLLER 54 B. VERILOG TESTBENCH 62

C. XILINX REPORTS 68 D. C432 VERILOG CODE 91

v

ABSTRACT

State of the art developments in the semiconductor manufacturing processes, integrated chip design methodology, availability of thousand plus pin integrated circuit (IC) packaging options and efficient IC test techniques have contributed immensely towards the integration of entire system on a chip.

These System-On-Chip (SOC) devices can include multiple microprocessors, various types of memories such as SRAM, Flash and ROM, Digital Signal Processor(s), dozens of IP blocks and user defined logic.

Various SOC test techniques have been innovated in the last decade to test complex mixed signal systems on a chip in a cost effective manner. The test industry has made great strides in developing new automated test equipment which can test logic, memory and analog components of the chip via external interface to the IC. Advances in the Built-In-Self-Test (BIST) techniques has enabled IC testing using a combination of external automated test equipment and BIST Controller on the chip.

vi

The power consumption of the chip during manufacturing test can

be significantly higher than the power consumption of the chip in its target system. This increase in the power consumption can be attributed primarily to on-chip extremely random test pattern generation.

This thesis probes into the various IC test approaches such as

external, internal and embedded with specific investigation into the low power test stimulus generation. A new low power pattern generation technique is implemented. Conventional and low power test patterns are applied on an industry standard ISCAS-85 c432 27-channel interrupt controller circuit and average power consumption is measured. The results indicate 60% lower power consumption by the circuit using the new approach for an identical fault coverage of 98% in both cases.

vii

LIST OF TABLES 2.1 ITRS Roadmap by Product 12 3.1 Present/Next State of the Flip-Flops 22 5.1 Power Consumption Analysis 46

viii

LIST OF FIGURES 2.1 IC Design Process 9 3.1 Test Methodology 17 3.2 IEEE 1149.1 TAP 21 3.3 LFSR 22 3.4 Companion Matrix 23 3.5 Maximal Length LFSR 24 4.1 LP-LFSR 28 4.2 ISCAS-85 c432 27-Channel Interrupt Controller 35 4.3 ISCAS-85 c432 M1 36 4.4 ISCAS-85 c432 M2 37 4.5 ISCAS-85 c432 M3 37 4.6 ISCAS-85 c432 M4 38 4.7 ISCAS-85 c432 M5 38 5.1 8-bit LFSR 40 5.2 8-bit Maximal Length LFSR 40 5.3 LP-LFSR Pattern Simulation 41 5.4 Power Estimation Flow 42

ix

CHAPTER I

INTRODUCTION

Project Motivation

System-On-Chip (SOC) Integrated Circuits (IC’s) are designed and

manufactured to meet application specific functional requirements. Some

examples of applications are camera-on-a-chip, MP3 player, etc. These

functional requirements often need to be balanced with the desired IC

performance, maximum allowable power consumption and overall packaged

and tested IC cost.

Generally total power consumption of the device is a sum of the

power consumed by the core and I/O’s13. Appropriate package

attributes such as the material and thermal properties need to be

selected to ensure maximum heat dissipation of the die through the

package.

IC Architects normally have a specific power consumption budget for

the SOC based on the overall system level power budget. Functional

operation of the device in a system usually consumes power either at or

under the budgeted power for the IC. However the same device under

1

Manufacturing test especially with BIST controller and random pattern

generator can consume more power than the budgeted power1.

This increase in the power consumption of the IC in the test mode is

well known in the industry to cause sudden un-repairable device failures

resulting in significant manufacturing fall-out directly impacting the cost of

the IC.

Today a combination of external Automated Test Equipment (ATE)

and internal BIST (Built-In-Self-Test) techniques are used to ensure the

highest possible fault coverage of the device at the lowest possible cost2,3.

IC testing using exclusively external ATE’s can require SOC

architects to allocate a fairly large number of pins of the device to

invoke the test procedure and run vectors into and through the

various blocks of the device such as memory, user defined

logic, dedicated functional macros, etc. Combination of external

ATE’s and internal BIST however can result in, utilizing far fewer external

pins on the IC but at the cost of embedding test logic inside the device4.

2

Project objectives

Test Pattern generation has long been carried out by using

conventional Linear Feedback Shift Registers (LFSR’s5). LFSR’s are

a series of flip-flop’s connected in series with feedback taps defined by the

generator polynomial6. The seed value is loaded into the outputs of

the flip-flops. The only input required to generate a random sequence is an

external clock where each clock pulse can produce a unique pattern at the

output of the flip-flops.

This random sequence at the output of the flip-flops can be used as a

test pattern. The number of inputs required by the circuit under test must

match with the number of flip-flop outputs of the LFSR. This test pattern is

run on the circuit under test for desired fault coverage.

The power consumed by the chip under test is a measure of the

switching activity of the logic inside the chip which depends largely on the

randomness of the applied input stimulus. Reduced correlation between the

successive vectors of the applied stimulus into the circuit under test can

result in much higher power consumption by the device than the budgeted

power. A new low power pattern generation technique is implemented using

a modified conventional Linear Feedback Shift Register7.

3

Conventional as well as low power test patterns are run on an industry

standard benchmark circuit. The instantaneous and peak power

consumption8 of the circuit is measured using industry standard Xilinx

tool called xPower and it is demonstrated that the new low power approach

results in significantly lower power consumption by the circuit under

test compared with the power consumption by the circuit using the

conventional pattern for the same fault coverage.

Thesis outline

Chapter 2 reviews SOC’s and their attributes with some insight into

the application specific Intellectual Property (IP) requirements. It also

provides an overview of the IC manufacturing processes, design/test tools

and methodology, discusses the various types of power consumed by the

device during normal operation and under manufacturing test. It also

provides a brief insight into the chip assembly process.

Chapter 3 investigates into the IC test tools and methodology

particularly external, internal and a combination of external/internal

approaches. The concept of BIST architecture and its components is

explained along with the explanation of LFSR, a circuit very commonly

4

used to generate random test patterns. The correlation of the LFSR, its

characteristic polynomial and matrix theory is described9,10.

Chapter 4 begins with a description of a pattern generated using a

conventional LFSR. It explains in detail the idea behind the low power

pattern generation in particular the low power technique designed using two

levels of logic between the outputs of the LFSR and the actual outputs

coming out of the second level of logic. Standard tools such as Verilog

HDL, Xilinx, and Mentor’s Modelsim are used for design description,

synthesis, simulation and power consumption estimation. A brief

background of the commonly used industry standard benchmark circuits is

also provided.

Chapter 5 begins with the methodology used to determine the power

consumption by the c432 benchmark circuit using the conventional pattern.

It explains the methodology used for computing power consumption by the

ISCAS-85 benchmark circuit c432 (27-channel interrupt controller) using

the low power pattern. A comparison of the circuit power consumption is

discussed between the two techniques.

Chapter 6 provides some recommendations on future work.

5

CHAPTER II

SOC BACKGROUND

SOC Attributes

SOC’s typically integrate multiple Microprocessors, various types of

memories such as SRAM, ROM, Flash, user defined logic, etc. Most SOC’s

are heavily populated with multiple instances of memory. Also included can

be IP macros such as Digital Signal Processors, Analog to digital

converters, etc11.

SOC’s typically contain multiple types of I/O’s ranging from standard

CMOS, LVTTL to high speed I/O’s such as LVDS (Low voltage differential

signal).

The pin count can range from a few hundred pins to over a thousand

with custom designed packages including multiple layers of substrate.

SOC’s are solution driven with the intent of providing a single chip solution

for particular applications such as digital cameras, MP3 players, storage

drives, printers, networking, etc. SOC’s for the Consumer electronics

typically include mixed signal components such as A/D, D/A,

multiple instances of SRAM, Flash, ROM and user defined logic.

6

Networking and Storage applications tend to be extremely compute

intensive and therefore it is not uncommon to find these devices containing

multiple microprocessor cores along with many megabits of memory and

high speed I/O’s operating in the giga-bit per second range.

Increasing the complexity of the SOC designs besides higher level of

IP integration are other factors such as multiple clock domains ranging from

a few kHz to as high as few GHz. Each clock domain is typically responsible

for running a specific portion of the chip12.

Power consumption of the device normally includes power consumed

by the core of the chip plus power consumed by the I/O’s13. Most SOC die

are packaged in multiple substrate packages with some level of signal

routing in the package substrates. Various types of packages such as Quad-

Flat-Packs, Ball Grid Arrays, etc can be custom designed (e.g. Plastic or

Ceramic) to meet the required power dissipation of the SOC die.

SOC Design Tools and Methodology

Generally the architecture of the entire SOC is designed and simulated

by chip architects. Front end designers are involved in converting the

7

architecture level IC requirements to detailed circuit level descriptions using

design description languages such as Verilog, VHDL, etc. Depending

on the complexity of the overall IC project, it is not uncommon to find front

end design teams ranging from ten’s of engineers to a few hundred spending

anywhere from 6 months to a year on the entire device design.

Back-end Design Engineering typically entails converting the circuit

level description to a physical description format used by the foundries for

IC Manufacturing. Again this task can also require a large number of

engineers depending on the physical size of the chip.

The entire SOC is simulated at an architecture level for the required

functional performance. Individual modules are synthesized and verified for

their respective functionality. Design verification is performed iteratively

before and after each stage of the entire IC design (Front-End to Back-End)

process. Verification results are compared between the pre and post

processing of each design stage to ensure compliance to the required

specification and easier root cause analysis in case of any errors.

Figure 2.1 below shows typical IC Design methodology before the

formal hand-off to the foundry for manufacturing. The methodology

includes Design Description, Logic Synthesis and Optimization, Pre-Layout

8

Simulation, Place and Route, Post Layout Simulation, DRC/LVS, GDS11

and mask generation.

Figure 2.1 IC Design Methodology

9

It is important to note that continuing advances in the inclusion of the

advanced Manufacturing process parameters in the front end IC Design

libraries and tools is expected to shrink the gap between the Front-end and

Back-end design tasks. This can result in requiring Front-end Design

Engineers to perform their tasks conforming to not only circuit design

limitations but also compliant to manufacturing constraints.

In addition to design for manufacturing, design for test approach is

mandating the chip design and test architects to include built-in self-test

controllers and test pattern generation inside the chip. While this mandate

can result in many benefits such as lower cost of test, etc it can also increase

the die size and power consumption.

SOC Power Consumption

Estimating the IC power budget involves maintaining perspective of

several technical and business factors such as process technology, cell

design libraries, pin-out and package constraints, logic and IP macro clock

domains, cost and time pressures, etc.

10

IC architects are required to select the optimum combination of these

elements to be able to achieve not only a functional device but also cost

competitive and meeting customer schedule.

Total power consumption of the CMOS device is the sum of static

power, dynamic power, leakage and short crcuit11. Static power can be

defined as the power consumed by the CMOS gate under no switching

activity. It is normally attributed to the leakage currents in the device.

Dynamic power on the other hand is a direct result of the switching

activity of the gate and is generally most of the power consumed by the

device. The more the gates toggle or change states under various load

conditions, the more dynamic power is consumed. Short circuit power of the

cell is caused by the temporary short circuit between the N and P transistors

of the gate during logic transitions.

SOC Manufacturing Processes

As evident in Table 2.1 below CMOS Manufacturing process

technology developers have made remarkable strides in shrinking the gate

length with majority of the present day SOC’s manufactured in 0.18 and

11

smaller process geometries. It is common to find devices using both Al and

Cu interconnects with low-k dielectric materials.

Table 2.1 ITRS roadmap by Product

Year of Production 2005 2006 2007 2008 2009 2010 2011 2012 2013DRAM stagger-contacted Metal 1 M1 1/2 pitch (nm) 80 70 65 57 50 45 40 36 32MPU/ASIC stagger-contacted Metal M1 1/2 pitch (nm) 90 78 68 59 52 45 40 36 32Flash Uncontacted Poly Si 1/2 pitch (nm) 76 64 57 51 45 40 36 32 28MPU Printed Gate Length (nm) 54 48 42 38 34 30 27 24 21MPU Physical gate Length (nm) 32 28 25 23 20 18 16 14 13

Sub nanometer manufacturing technologies have enabled millions of

transistors to be packed in few millimeter squared die sizes. The ability to

manufacture these many transistors has driven the integration of entire sub-

systems and in most cases complete systems on a chip.

On the other hand EDA tool developers have kept up with their pace

on developing advanced tools linking Design for Test and Design for

Manufacturing. More than a decade old concept of Design for Test has been

extended to Design for Manufacturing.

Today there are tools available to validate the Manufacturing viability

of the designs before getting to the Foundry18.

12

The advanced ability to estimate the yield of the chip with circuit

design as well as manufacturing constraints has resulted in significant cost

savings in the entire supply chain of IC design and manufacturing.

The cell library and IP developers have diligently kept up with the

design and development of the various types of libraries such as low power,

small size, etc and cores such as Microprocessors, DSP’s, Memories, etc

respectively. The ability to select and integrate pre-verified silicon proven

IP blocks on a single substrate has made significant contribution toward the

design and production of entire systems on a chip for a variety of market

applications.

SOC Test and Assembly

The scope of IC test can range from wafer level (ensure good wafer)

testing to individual die on the wafer and at the packaged chip level. The

selection of a type and/or a combination of these tests can be driven by

multiple factors such as the complexity of the chip, test cost, price of the

chip as determined by the market, etc. For example it may be cost

prohibitive to run very small chip (order of few thousand gates in a small 48-

pin QFP package targeted for market price of sub $1) through each of these

13

phases. The total test cost for these phases combined can easily surpass the

individual die or package cost resulting in the price of the chip deemed un-

bearable by the market3.

Design for Test is a common approach used in architecting and

implementing complex SOC’s. IP level (Microprocessors, A/D, PLL,

Memory, etc) functional verification and manufacturing tests are often

performed by the IP providers before the IP is integrated into the SOC.

SOC Designers however still need to include test logic on the chip to be

able to test the IP in the overall system design environment.

User-defined Logic is commonly verified using an FPGA before

integrating it on the chip. Again it is incumbent upon the SOC design team

to include logic for test on the chip to test user defined logic along with the

other blocks of the chip.

A combination of external testing using Automated Test Equipment

and internal testing using memBIST , LogicBIST, IPBIST, SCAN, etc

techniques are used to verify the overall functionality of the SOC.

Die and Package assembly is a function of the die size and type of

package. Commonly used package types include QFP’s and BGA’s. The

cavity of the package is indicative of the die size that can be accommodated

14

in the package. SOC suppliers can choose to test the IC at the package level

and ignore tests at the wafer and/or die level. This is primarily done to save

costs. (SOC cost is the sum of the die, package and test/assembly cost).

15

CHAPTER III

SOC TEST

SOC Test Tools and Methodology

As noted in chapter 2 it is imperative to verify the functional and

manufacturing viability of the individual IP components before integrating

them into the SOC design. Most cores are offered with the wrapper logic

around the IP which is used as the interconnect between the design blocks.

Internal design details of IP macros are typically not shared by the IP

provider as that information is considered confidential.

SOC testing is best viewed as an iterative process comprised of a

series of tests. Figure 3.1 shows a test methodology. Either flat or

hierarchical approach can be used depending on the complexity of the device.

As the complexity of the device increases it is often recommended to test

individual components using Scan and/or BIST as opposed to testing the

entire design using a flat approach. The flat approach would essentially

flatten the entire design’s netlist, apply stimulus at the primary inputs of the

design and test outputs at the primary outputs. This approach does not

16

provide the ability to observe the logic at the interconnects between the

various blocks of the design.

Figure 3.1 Test Methodology

An advantage of testing the SOC using a hierarchical approach is its

inherent ability to isolate and correct the problem piecewise. Test input

stimulus is applied to a particular macro with the outputs observed and

verified.

17

External ATE testers can include Logic, Memory, Processor and

Mixed-signal test specific boards. Conventional Design for test approaches

include Scan and Built-In-Self test. Most SOC designs today however

include an embedded test approach which involves using a combination of

external low cost Digital tester and on-chip test logic for stimulus generation,

output analysis and compression, diagnostics, timing, power management,

etc14.

Test Approaches (External ATE, Conventional DFT and Embedded4 )

Embedded test is a natural evolution of the two distinct approaches

discussed thus far namely external ATE and DFT. External ATE approach

requires a mix of very expensive low/high speed testers with varying

bandwidth. These testers can be configured to provide function specific test

ability for high speed logic, memory, analog to digital converters, etc.

DFT approach on the other hand is predominantly based on using

Scan and BIST test architectures. Scan test involves replacing the generic

flip-flops of the design with scan enabled flip-flops along with the insertion

of multiple scan chains around the design. Test input stimulus can be

18

propagated either through the individual portion of the design or the entire

device for functional verification.

Embedded test integrates the high speed and high bandwidth portions

of the external ATE directly into the IC and can be considered as the main

objective of the embedded test approach. Automatic test pattern

generation/Fault Simulation tools can be used to generate, integrate, analyze

and verify test pattern development.

One of the key benefits of the embedded test is in the on-chip test data

generation which reduces the volume of external patterns and can be

customized per the IP block type in the SOC. On-chip go/no-go and data

compression reduces ATE data logging. On-chip timing generation achieves

true at speed tests that can be scaled to match manufacturing process

technology performance. The downside of on-chip data generation however

is the increase in the power consumption of the device in the test mode.

Built-In Self Test (BIST)

BIST is a hierarchical DFT strategy that reduces the need for external

test. With BIST a micro-tester complete with a pattern generator is brought

onto the chip enabling the chip to test itself. Although the micro-tester

19

requires more silicon area, the savings realized through automation of the

testing process makes this DFT method very attractive.

BIST logic is composed of pattern generation, pattern capture and

compare and self test control. BIST can be used for low speed as well as

high speed testing. BIST uses on-chip controllers for memory, logic, etc.

These controllers are typically accessed via an external interface defined by

the various IEEE standards. IEEE standard 1149.1 as shown in Figure 3.2

defines the test access port composed of 5 external pins for initializing BIST

operation, monitoring and reading results.

The benefits of BIST are higher quality testing, faster time to market

and lower costs. Chips can be tested at speed without incurring yield losses

because of tester inaccuracy. BIST automates a higher degree of the test

development process and simplifies the development of test programs. BIST

reduces the dependency on expensive ATE. High end ATE costs are

approximately five million U.S. dollars. This need is attributed to more

memory to store large patterns, faster pin electronics, BIST solves the ATE

cost problem by moving data directly onto the chip4.

20

Figure 3.2 IEEE 1149.1 TAP

BIST Pattern Generation using LFSR

Linear Feedback Shift Register is a circuit consisting of flip-flops

connected in series with each other. The output of one flip-flop is connected

to the input of the next flip flop and so on. The feedback polynomial which

is also known as the characteristic polynomial is used to determine the

feedback taps which in turn determines the length of the random pattern

generation.

An example below in Figure 3.3 is used to illustrate a correlation

between the LFSR, its characteristic polynomial and matrix theory. In the

circuit the feedback taps are shown to be from the output of the 4th and 1st

register.

21

Figure 3.3 LFSR

These taps are indicative of the generator polynomial. According to

this polynomial the present and the next state of these registers are shown in

Figure 3T(R1, R2, R3, R4 and R1=R1⊕R4, R2 = R1, R3 = R2 and R4 =

R3).

Table 3.1 Present/Next State

Present State

Next State

R1 R1 ⊕ R4 R2 R1 R3 R2 R4 R3

Using the matrix theory the companion matrix required for relating

the present to the next state is depicted in Figure 3.4 below. The actual

sequence of the LFSR is represented as BT, BT2, BT3, ….where B is the

22

seed vector. The determinant of the T matrix is called the characteristic

polynomial and the generator polynomial is the inverse of the characteristic

polynomial.

1 0 0 1

1 0 0 0

0 1 0 0

0 0 1 0

Figure 3.4 T Companion Matrix

Det(T) = [xI – T] {Characteristic Polynomial}

Where I is the identity matrix

Generator Polynomial = Inverse of the Characteristic Polynomial

As an example the characteristic polynomial for the above circuit is =

X4 + X3 + 1 and the generator polynomial is represented as X4 +X +1.

Normally the feedback taps are selected such that entire sequence is

generated including all zeros and one’s. The generation of all zero’s pattern

requires an additional NOR gate whose inputs are the outputs of all flip-

23

flops in the LFSR. The output of the NOR gate is fed into the input of the

first flip-flop in the circuit as shown in Figure 3.5.

Figure 3.5 Maximal Length LFSR

The outputs of the LFSR are initially loaded with a combination of 1’s

and 0’s normally referred to as the seed vector. Proper selection of the

generator polynomial is important in order to ensure the generation of the

entire sequence. Common Clock signal is applied to the entire chain of flip-

flops which essentially enables the propagation of the logic values present at

the inputs to the flip-flop outputs. These random outputs are used as the

input stimulus for circuit to be tested.

Normally this random pattern can be propagated through a known

24

good circuit and the output of the circuit is captured using a MISR (Multi-

Input Shift Register). The MISR output also known as the good signature is

then used to compare with the signature obtained for other similar circuits.

One of the drawbacks of generating a pattern using the above

approach is the reduced correlation15 between the bits (output bits of the

LFSR) of the successive vectors. This can attribute to one of the key

differences between the vectors used for functional verification of the IC in

the system environment compared to the vectors used in the manufacturing

test environment.

In a functional operation environment, the input stimulus is generated

by the component(s) of the system interfacing with the device under test and

therefore can have better correlation between the successive vectors.

Additionally the number of vectors generated in a functional test

environment can be much lower than the number of vectors generated by the

LFSR. This increase in the number of test vectors combined with reduced

correlation between the bits can result in significant increase in the switching

activity of the circuit under test and therefore increased power consumption

of the device in the Manufacturing Test environment.

25

The increased power consumption by the device in the manufacturing

test environment therefore can in most cases exceed the maximum power

consumption specification of the IC resulting in un-repairable device failures

begins with a pattern generated using a conventional LFSR causing

significant loss of yield.

26

CHAPTER IV

LOW POWER PATTERN GENERATION

Idea behind low power test pattern generation

One way to improve the correlation between the bits of the successive

vectors is to avoid frequent transitioning of the logic levels (1 0 or 0 1)

of the primary inputs.

The new approach entails inserting 3 intermediate vectors between

every two successive vectors. The total number of signal transitions between

these 5 vectors is equal to the total number of signal transitions between the

2 successive vectors generated using the conventional approach. This

reduction of signal transition activity in the primary inputs reduces the

switching activity inside the design under test and therefore results in

reduced power Consumption by the device under test.

The additional circuitry used to accomplish the generation of the 3

intermediate vectors is minimal at best consisting of few logic gates.

The pattern generation controller which is designed using Verilog as

shown in Appendix A can be very easily modified for the required number

of LFSR outputs.

27

The number of LFSR outputs required is driven by the number of test

inputs required for circuit under test.

The technique of inserting 3 intermediate vectors is achieved by

modifying the conventional LFSR circuit with two additional levels of logic

between the conventional flip-flop outputs and the low power outputs as

shown in Figure 4.1. The first level of hierarchy from the top down includes

logic circuit design for propagating either the present or the next state of the

flip-flops to the second level of hierarchy. The second level of hierarchy is a

multiplexer function that provides for selecting between the two states

(present or next) to be propagated to the outputs as low power output.

Figure 4.1 LP-LFSR

28

In the simulation environment, the outputs of the flip-flops are loaded

with the seed vector. The feedback taps are selected pertinent to the

characteristic polynomial x8 + x + 1. Only 2 inputs pins, namely test enable

and clock are required to activate the generation of the pattern as well as

simulation of the design circuit. It is also noteworthy here that the

intermediate vectors in addition to aiding in reducing the number of

transitions can also empirically assist in detecting faults just as good as the

conventional LFSR patterns.

Description of the technique to produce low power pattern for BIST

The following is a description of a low power test pattern generation

technique as depicted in the 9-bit LFSR based schematic in Figure 4.1.

Verilog based test bench as shown in Appendix B is used in assigning the

initial output states (0100 1011) of the 9-bit LFSR. The feedback taps are

designed for maximal length LFSR generating all zeros and all one’s as well.

The first step is to generate T1, the first vector by enabling (clocking)

the first 4-bits of the LFSR and disabling (not clocking) the last 4 bits. This

Shifts the first 4 bits to the right by one bit. The feedback bits of the LFSR

are the outputs of the 8th and the first flip-flop. The output of the 8th flip-flop

29

is 1 and the output of the first flip-flop is 0. The exclusive-or of the

8th-flip-flop (logic 1 in this case) and the first flip-flop(logic 0 in this case) is

input (1 EXOR 0 = 1 into the first D flip-flop. The new pattern in the first

four bits of the LFSR is 1010. Note that the shaded register is clocked along

with the first 4 bits of the LFSR. So the input of the shaded flip-flop is the

output of the 4th flip-flop which in this case is 0.

Also note that prior to the first clock, the input of the shaded register

was the seed value of the 4th flip-flop at the output of the 4th flip-flop which

in this case is 0. So after the first clock this value of 0 will now appear at the

output of the shaded flip-flop. In other words the value of the 4th output is

stored in this shaded register and is used in the next few steps.

The first 4 shifted bits of the LFSR and the last 4 un-shifted bits (i.e.

the seed value) are propagated as T1 (1010 1011) to the final outputs.

Next few steps involve generating the 3 intermediate patterns from T1.

These patterns are defined as Ta, Tb and Tc.

Ta is generated by maintaining (disabling the clock to the first 4 bits)

the first four bits of the LFSR outputs (as is from T1) as the final first four

low power outputs 1010. Note that the clock to the last four bits of the LFSR

is also disabled. The last four bits however are the outputs from

30

the injector circuits. The injector circuit compares the next value

(@ the input of the D-flip-flop) with the current value (@ the output of the

D-flip-flop).

According to T1, the outputs (current values) of the last 4 bits of the

LFSR are 1011. The next values are the values at the inputs of the D-flip-

flops which in this case are 0101. Compare the current values (1011) bit by

bit with the next values (0101). If the values bit by bit are not the same then

use the random generator feedback R (in this case is logic 1) as the bit value

as shown in the schematic above. If however both values bit by bit are the

same then propagate that bit value to output as opposed to the R bit. This

bit by bit comparison gives us the last four bits of Ta to be 1111. Therefore

Ta = 1010 1111.

Next step is to generate Tb. Shift the last 4 flip-flops to the right one

bit but do not shift the first 4 flip-flops to the right. The clock to the first 4

bits plus the shaded flip-flop is disabled. The clock to the last 4 bits is

enabled.

Propagate the outputs of the flip-flops of the entire LFSR as opposed

to the outputs of the injection circuit to the outputs (low power). The

injection circuits are disabled.

31

As in Ta, maintain the first four LFSR outputs (1010) as the low

power outputs. Again from Ta, the inputs of the last four D flip-flops

from the previous step (generating Ta) are 0101. Also note that the output of

the shaded register is 0 from the previous step (generating Ta). Therefore the

input of the 5th flip-flop is a 0. The outputs of the last 4 flip-flops are

0101 resulting in Tb = 1010 0101.

The 3rd intermediate vector Tc is generated via disabling the clock to

the entire LFSR. Propagate the first 4 outputs from the injection circuit as

the first 4 low power outputs and maintain the last 4 low power outputs the

same as Tb. Generating injection circuit outputs for Tc is conceptually the

same as explained above in generating Ta. Current values (@ the outputs of

the flip-flops) of the first four flip-flops are compared with the next values

(@ the inputs of the flip-flops) of the flip-flops.

The feedback from the 8th flip-flop is 1 (please see generating Tb).

Therefore the logical feed forward value of R is 1. The feedback value from

the first flip-flop is also 1 as per the current values above. The exclusive

or of two ones is a 0. Therefore the input to the first flip-flop is a 0 which is

also the next state of the first flip-flop. Hence the next values are 0 for the

first flip-flop and 101 for the 2nd, 3rd and 4th flip-flop respectively. The next

32

values are 0101.

The first four outputs from the injection circuit are 1111. The last 4

outputs are the same as Tb which are 0101 resulting in the 3rd and final

intermediate vector Tc = 1111 0101.

Generating T2 is quite similar to generating T1. As in Tc the outputs

of the last four LFSR flops are 0101. The outputs of the first 4 flip-flops of

the LFSR are the current values which are 1010. Therefore the seed vector

for generating T2 is 1010 0101.

Shift the first four bits of the LFSR plus the shaded flip-flop. Do not

clock the last four flip-flops. Propagate the outputs of the entire LFSR to the

final low power outputs.

The output of the 8th flip-flop from the previous step (generating Tc)

is a 1 and the output of the first flip-flop from the previous step (generating

Tc) is also a 1. The exclusive or of the output of the 8th flip-flop and the first

flip-flop is 0.

Therefore the input to the first flip-flop will be a 0. The inputs to the

2nd, 3rd , 4th and the shaded flip-flops are 1010. These are also the current

values from the previous step (generating Tc). Shifting the first four flip-

flops of the LFSR to the right by one bit results in 0101 as the outputs of the

33

first four flip-flops. Therefore T2 generated is 0101 0101. This concept of

low power pattern generation is extended to 36-bits required for the design

circuit indicated in section 4.3.

Benchmark Design Circuits

Several Industry standard benchmark circuits such as ISCAS-85,

ISCAS-89, etc can be used to test new design, test and manufacturing

approaches and technologies. Following is a brief description of one of the

ISCAS-85 circuits used for the purpose of testing the new low power pattern

generation scheme described above.

c432 is a 27-channel interrupt controller. The input channels are

grouped into three 9-bit buses (we call them A, B and C), where the bit

position within each bus determines the interrupt request priority. A forth 9-

bit input bus (called E) enables and disables interrupt requests within the

respective bit positions. Figure 4.4 below shows the c432 circuit. Figures 4.5

to 4.9 below show the logic of the underlying modules.

34

Figure 4.4 ISCAS-85 C432 27-channel interrupt controller

The interrupt controller has three interrupt request buses A, B and C,

each having nine bits or channels, and one channel-enable bus E. The

following priority rules apply: A[i] > B[j] > C[k], for any i, j, k; i.e., bus A

has the highest priority and bus C the lowest. Within each bus, a channel

with a higher index has priority over one with a lower index; for example,

A[i] > A[j], if i > j. If E[i] = 0, then the A[i], B[i], and C[i] inputs are

disregarded.

35

The seven outputs PA, PB, PC and Chan[3:0] specify which channels

have acknowledged interrupt requests. Only the channel of highest priority

in the requesting bus of highest priority is acknowledged. One exception is

that if two or more interrupts produce requests on the channel that is

acknowledged, each bus is acknowledged. For example, if A[4], A[2], B[6]

and C[4] have requests pending, A[4] and C[4] are acknowledged. Figure

4.9 is a 9-line-to-4-line priority encoder.

Figure 4.5 ISCAS-85 c432 M1

Figure 4.6 ISCAS-85 c432 M2

36

Figure 4.7 ISCAS-85 c432 M3

Figure 4.8 ISCAS-85 c432 M4

37

Figure 4.9 ISCAS-85 c432

38

CHAPTER V

RESULTS AND DISCUSSION

Simulation using standard LFSR pattern

The standard 36-bit pattern is generated using the LFSR configuration

as shown in figure 5.1 below. The schematic in the case of conventional

pattern generation consists of 36 flip-flops connected in series. The design is

modified as indicated in figure 5.2 below with feedback taps to generate a

maximal length pattern generator including all 0’s and 1’s. The number of

vectors expected in this case are 236. The outputs of the 36-bit LFSR are

used as the inputs to the c432 ISCAS-85 interrupt controller design circuit.

A common clock is supplied to all flip-flops. A seed value is assigned to the

output of each flip-flop. Each clock pulse thereafter shifts the logic value

present at the input of the flip-flop to its output.

39

Figure 5.1 8-bit LFSR

Figure 5.2 Maximal 8-bit LFSR

Simulation Using LP-LFSR

LP-LFSR pattern is generated as shown in Figure 5.3 below. The

simulation report confirms the number of signal transitions between the bits

of the successive vectors to be the same for both patterns namely,

conventional and LP-LFSR.

40

Figure 5.3 LP-LFSR Pattern Simulation

Power consumption using standard conventional pattern

The methodology used to estimate the power consumption is similar to

the one used for the low power pattern generator. As shown in figure 5.4 the

design circuit is simulated in the Xilinx ISE development environment using

Mentor Graphics’ ModelSim. The number of test vectors is restricted in

order to contain the Verilog Core Dump file to a manageable size for power

consumption analysis.

41

Fig 5.4 Power Estimation Flow

42

The VCD file contains the switching activity of the design circuit for the

number of test vectors. The number of test vectors is obtained from a Fault

simulation tool called TetraMax from Synopsys. This tool takes the VCD

file as the input file along with the c432 interrupt controller design file and

produces the number of test vectors required for the desired fault coverage.

Another way of generating specific number of vectors is by using the

clock period and simulation time. For instance if the clock period is 60ns

and the simulation time is 60us. The number of vectors produced will be

60us/60ns = 1000.

Using the standard pattern, the ATPG tool generates 330 vectors for

98% fault coverage which translates to approximately 16mw power

consumption by the c432 circuit.

Power consumption using low power pattern

The key to achieving Low power consumption in System-On-Chip

devices is by reducing the switching activity in the device under test. The

low power technique described in chapter 4 improves the correlation

between the signals of the successive vectors (i.e. input stimulus to the

43

circuit under test) resulting in reduced transitions of the primary inputs

hence reducing switching activity inside the circuit under test.

The methodology used in estimating the power consumption16,17 of

the device under test includes the generation of the 36-bit low power pattern,

synthesizing the c432 circuit using generic libraries, running the 36-bit

pattern on the c432 circuit and computing the power consumption using a

power estimation EDA tool.

Circuit Simulation is implemented using Mentor’s ModelSim tool in

the Xilinx ISE development environment. It is important to restrict the

simulation time (i.e. number of test vectors) to a few microseconds in order

to contain the VCD file to a manageable size for the purpose of evaluating

the switching activity. Xilinx xPower tool is used to read in the VCD file for

power consumption estimation. TetraMax was used to determine the number

of test vectors required for the desired fault coverage.

Power consumed by the c432 circuit is observed to be 10mw using

370 vectors for 98% fault coverage. Detailed reports on synthesis,

simulation and power estimation are included in Appendix C.

Power Consumption Comparison (Standard LFSR vs LP-LFSR)

44

Two test benches are designed using Verilog as labeled in Appendix B.

The first test bench uses a conventional test pattern generator and the

second test bench uses a low power pattern generator. Both test benches are

used to simulate a common design circuit which in this case is an industry

standard 27-channel interrupt controller benchmark circuit. Verilog code for

c432 is included in Appendix D.

Both test benches are designed to use the same pre-defined clock

period as well as identical simulation time. This ensures the same number of

test vectors generated by both test benches. The number of gates used by the

interrupt controller are 250 as indicated by the synthesis reports from the

Xilinx development environment. Logic gates used by the conventional test

bench are 60 and the number of gates used by the low power test bench are

135.

TetraMax ATPG and Fault simulation tool is used to estimate the

number of test vectors required for 98% fault coverage of the interrupt

controller. The tool generated 330 vectors for the conventional test bench

and 370 vectors for the low power test bench. Both test benches produced

almost the same number of test vectors for the desired fault coverage thus

demonstrating about the same test time used in both cases.

45

The two VCD files (for conventional and low power pattern)

containing the interrupt controller’s switching activity were used for power

consumption estimation by Xilinx xPower power analysis tool.

xPower calculates the average power consumed by the circuit for each

test vector applied by observing the logic value at each internal and external

node of the circuit. The transition in the logic value at each node (1 → 0 or 0

→ 1) results in the dynamic power consumption by the gate of the Xilinx

Spartan 2 device. Total power consumed by the circuit is the sum of the

power consumption by the circuit for each test vector.

The reported power consumption estimates as indicated above

demonstrates approximately 60% lower power consumption by the interrupt

controller using the low power test bench as compared with the conventional

pattern. This result demonstrates lower number of logic transitions at the

internal and external nodes of the test circuit. The difference in the power

consumption of the test logic between the two approaches (65 gates versus

135 gates is negligible).

46

Table 5.1 Power Consumption Comparison

Fault Coverage # of Test Vectors

# of Gates in the

Test Circuit

# of Gates in the Test

Controller Average Power Consumption

Conventional

The configurable logic blocks and input/output blocks used in most

field programmable gate arrays such as the Spartan 2 device are typically not

optimized for lowest power consumption compared with some options of the

gate array and Standard cell products. Therefore it is possible to achieve

even lower power consumption by the circuit in an ASIC implementation

compared with an FPGA.

Summary and Conclusion

The System on a chip revolution challenges both design and test

engineers especially in the area of power dissipation. Generally the chip

consumes more power in the manufacturing test mode than in normal

operation mode in its targeted system. The increase in the power

LFSR 0.98

330.00

250

65 16mW

LP-LPSR 0.98

370.00

250

130 10mW

47

consumption can result in un-repairable damages in the chip directly

impacting the overall yield and cost.

This thesis investigates the fundamental process used for IC Design, Test

and Manufacturing including design entry, tool flow methodology and hand-

off to Manufacturing. Specific detailed attention is focused on IC

verification and test.

Design-For-Test and Design-For-Manufacturing is the mainstream

approach today for IC Design. This approach is mandating the entire SOC

development team to collaborate very closely with each other in clearly

articulating adequate test requirements and methodology as well as ensuring

the manufacturability of the chip.

Various test methodologies such as external (ATE based), DFT-

SCAN/BIST and embedded (combination of low cost external tester and

SCAN/BIST) approaches are studied. The embedded approach is found to be

prevalent in SOC testing.

It may be easier, for the large Semiconductor component companies

when compared with smaller Fabless companies, to justify the cost of

expensive external ATE systems due to the higher utilization rate by the

48

former and inherent flexibility in expensive ATE’s to integrate test (e.g.

memory, mixed-signal, etc) specific electronics. Other trade-off factors

such as the impact of the number of pins required in the device for test,

external versus internal pattern generation, etc need to be carefully evaluated

for the most optimum cost versus performance test solution.

Including SCAN/BIST on the chip tends to increase the die size by a

small percentage and the power consumption of the chip. The increase in the

power consumption is attributed primarily to the increase in the circuit’s

switching activity. Random pattern generation theory is investigated along

with the correlation of the Linear Feedback Shift Register based PRPG,

matrix theory, characteristic polynomial and the generator polynomial.

A Technique to generate low power PRPG is implemented and

applied on an industry standard benchmark circuit for power consumption

estimation. The comparison of power consumption by the circuit

demonstrates 60% lower power consumed by the circuit when using low

power pattern as the input stimulus compared with the input stimulus

generated by the conventional LFSR based PRPG.

49

CHAPTER VI

RECOMMENDATIONS FOR FUTURE WORK

SOC designs are making a rapid shift from mostly digital to mixed

signal including millions of user defined logic gates and dozens of IP (Core

as well as I/O based). IC Verification and Test strategy needs to include

advanced controllers and pattern generators for testing digital as well as

analog components of the chip. Pattern generation inside the chip is well

known to cause increase in the power consumption of the IC during the

manufacturing test. New design and test techniques need to be investigated

to keep this increase in the power consumption by the chip as minimum as

possible.

The availability of advanced manufacturing process rules in the

design/verification libraries and tool flow methodologies is mandating the IC

front-end designers to verify the manufacturability of the chip much in

advance in the design process . Therefore development of the new SOC DFT

techniques needs to be compliant with the advanced DFM rules18.

50

SELECTED BIBLIOGRAPHY

1 1 Patrick Girard, “Survey of Low-Power Testing of VLSI Circuits, IEEE Design and Test of Computers, May-June 2002, Volume: 19 , Issue: 3, page(s): 80 – 90, ISSN: 0740-7475 2 2 S. Zhang, et. al, “Cost driven optimization of fault coverage in combined built-In-Self-Test/Automated Test Equipment Testing”, IEEE Instrumentation and Measurement Technology Conference, May 18-20, 2004 3 3 L. Ungar and T. Ambler, “Economics of Built-In-Self-Test”, IEEE Design and Test of Computers, Sept.-Oct. 2001, Volume: 18 , Issue: 5, page(s): 70 – 79, ISSN: 0740-7475 4 4 Benoit Nadeau-Dostie, “Design for AT-SPEED TEST, DIAGNOSIS and MESUREMENT, ISBN 0-7923-8669-8 5 5 T.Moon and W. Stirling, “ Mathematical Methods and Algorithms for Signal Processing”, ISBN 0-201-36186-8 6 6 A. J. van de Goor, “TESTING SEMICONDUCTOR MEMORIES theory and practice”, ISBN 90-80 4276-1-6 7 7 N.Ahmed, M. H. Tehranipour, M. Nourani, “Low Power Pattern Generation for BIST Architecture”, IEEE Circuits and Systems, 2004. ISCAS '04. Proceedings of the 2004 International Symposium, 23-26 May 2004, Vol. 2, pages 689-92 8 8 X. Zhang and K. Roy, “Peak Power reduction in low power BIST”, Quality Electronic Design, 2000. ISQED 2000. Proceedings. 20-22 March 2000, page(s): 425 – 432

51

9 9 G. Marsaglia and A. Zaman, “A New Class of Random Number Generators”, The annals of Applied Probability, 1991, Vol 1, No. 3, 462 – 480 10 10 G. Marsaglia and L. Tsay, “ Matrices and the Structure of Random Number Sequences”, Linear Algebra and its applications 67:147-156 (1985) 11 11 F. Nekoogar, “From ASICs to SOCs, A practical Approach”, ISBN 0-13-033857-5 12 12 Barabara Chappel, “The fine art of IC design”, IEEE Spectrum, July 1999, Volume: 36 , Issue: 7, page(s): 30 – 34, ISSN: 0018-9235 13 13 C. Wang and K. Roy, “Maximum Power Estimation for CMOS circuits using deterministic and statistic approaches”, 9th International conference on VLSI design, Jan 1996 14 14 E. Larson et, al, “Efficient Test Solutions for Core-Based Designs”, IEEE transactions on Computer aided design of integrated circuits and systems, vol. 23, May 2004 15 15 M.L. Mehta, “Some remarks on Random Number Generators”, Number theory and physics, 1990, Springer proceedings in Physics, Vol. 47, pages 253-259 16 16 F. Najm, “A survey of power estimation techniques in VLSI circuits”, IEEE Very Large Scale Integration (VLSI) Systems, Dec. 1994, Volume: 2 , Issue: 4, page(s): 446 – 455

52

17 17 F. Najm, “ Estimating power dissipation in VLSI circuits”, IEEE Circuits and Devices Magazine, July 1994, Volume: 10 , Issue: 4, page(s): 11 – 19 18 18 M. Schrader and R. McConnell, “SOC Design and Test considerations”, Design, Automation and Test in Europe Conference and Exhibition, 2003, page(s): 202 – 207, ISSN: 1530-1591

53

APPENDIX A

PATTERN GENERATION CONTROLLER

module top (Tte, Clk, resetn, out);

input Tte;

input Clk;

input resetn;

output [7:0] out;

wire En1;

wire En2;

wire Sel1;

wire Sel2;

wire anor;

wire [8:0] d;

//reg [8:0] q;

reg [8:5] q_upper;

reg [3:0] q_lower;

reg q_mid;

wire [7:0] out;

54

wire [7:0] qlfsr;

wire [7:0] dlfsr;

wire [7:0] rmuxout;

wire r;

lfsr_fsm lfsr_fsm_a

(.te(Tte), .clk(Clk), .en1(En1), .en2(En2), .sel1(Sel1), .sel2(Sel2));

always @(posedge En1 or negedge resetn)

begin

if (!resetn)

q_upper[8:5] <= 4'b0100;

else

q_upper[8:5] <= d[8:5];

end

always @(posedge En1 or negedge resetn)

begin

if (!resetn)

q_mid <= 1'b1;

else

q_mid <= d[4] ;

55

end

always @(posedge En2 or negedge resetn)

begin

if (!resetn)

q_lower[3:0] <= 4'b1011;

else

q_lower[3:0] <= d[3:0] ;

end

assign d[8:0] = {q_upper[8]^q_lower[0], q_upper[8:5], q_mid,

q_lower[3:1]};

//assign anor =

~(q_upper[8]|q_upper[7]|q_upper[6]|q_upper[5]|q_lower[3]|q_lower[2]|q_lo

wer[1]);

assign qlfsr = {q_upper[8:5],q_lower[3:0]};

assign dlfsr = {d[8:5],d[3:0]};

assign r = q_lower[0];

lfsr_andor_mux lfsr_andor_mux_a

(.qlfsr(qlfsr), .dlfsr(dlfsr), .r(r), .rmuxout(rmuxout));

assign out[7:4] = Sel1 ? q_upper[8:5] : rmuxout[7:4];

56

assign out[3:0] = Sel2 ? q_lower[3:0] : rmuxout[3:0];

endmodule

`timescale 1ns / 1ps

////////////////////////////////////////////////////////////////////////////////

// Company:

// Engineer:

// Create Date: 17:22:25 08/30/05

// Module Name: lfsr_andor_mux

// Revision 0.01 - File Created

// Additional Comments:

////////////////////////////////////////////////////////////////////////////////

module lfsr_andor_mux(qlfsr, dlfsr, r, rmuxout);

input [7:0] qlfsr;

input [7:0] dlfsr;

input r;

output [7:0] rmuxout;

wire [7:0] andout;

wire [7:0] orout;

assign andout[7:0] = qlfsr[7:0] & dlfsr[7:0];

57

assign orout[7:0] = qlfsr[7:0] | dlfsr[7:0];

assign rmuxout = r ? orout : andout;

endmodule

`timescale 1ns / 1ps

////////////////////////////////////////////////////////////////////////////////

// Module Name: lfsr_fsm

// Revision 0.01 - File Created

////////////////////////////////////////////////////////////////////////////////

module lfsr_fsm(te, clk, en1, en2, sel1, sel2);

input te;

input clk;

reg [2:0] count;

output en1;

output en2;

output sel1;

output sel2;

reg en1;

reg en2;

reg sel1;

58

reg sel2;

always @(posedge clk)

begin

if (te == 0)

count <= 3'b001;

else

count <= count + 1;

if (count >= 3'b100)

count <= 3'b001;

end

always @(posedge clk)

begin

if (te==1)

begin

if (count==3'b001)

begin

en1 <= 1'b1;

en2 <= 1'b0 ;

sel1 <= 1'b1 ;

59

sel2 <= 1'b1 ;

end

else if(count==3'b010)

begin

en1 <= 1'b0 ;

en2 <= 1'b0 ;

sel1 <= 1'b1 ;

sel2 <= 1'b0 ;

end

else if(count==3'b011)

begin

en1 <= 1'b0;

en2 <= 1'b1 ;

sel1 <= 1'b1;

sel2 <= 1'b1 ;

end

else if(count==3'b100)

begin

en1 <= 1'b0 ;

60

en2 <= 1'b0 ;

sel1 <= 1'b0;

sel2 <= 1'b1 ;

end

else

begin

en1 <= 1'b1;

en2 <= 1'b0 ;

sel1 <= 1'b1 ;

sel2 <= 1'b1 ;

end

end

end

endmodule

61

APPENDIX B

VERILOG TEST BENCH

`timescale 1ns / 1ps //////////////////////////////////////////////////////////////////////////////// // Company: // Engineer: // // Create Date: 17:08:47 12/08/2005 // Design Name: main // Module Name: testdec08.v // Project Name: projecta // Target Device: // Tool versions: // Description: // // Verilog Test Fixture created by ISE for module: main // // Dependencies: // // Revision: // Revision 0.01 - File Created // Additional Comments: // //////////////////////////////////////////////////////////////////////////////// module testdec08_v; // Inputs reg Clk; reg Reset; // Outputs

62

wire PA; wire PB; wire PC; wire [3:0] Chan; // Instantiate the Unit Under Test (UUT) main uut ( .PA(PA), .PB(PB), .PC(PC), .Chan(Chan), .Clk(Clk), .Reset(Reset) ); initial begin // Initialize Inputs Clk = 0; Reset = 0; // Wait 100 ns for global reset to finish #100; // Add stimulus here // Create a 60ns/16.7MHZ clock and run it for a few us Reset = 1; end always #30 Clk = ~ Clk; //Need to set sim time in modelsim for the VCD file - try atleast 6us // for sufficient switching activity. For 6us VCD file size is 26KB

63

initial begin $dumpfile ("conv.vcd") ; $dumpvars(1, testdec08_v.uut); end endmodule module conv36(clk, resetn, lout); input clk; input resetn; output [35:0] lout; wire znor,znor1,znor2; wire [35:0] d; reg [35:0] q; always @(posedge clk or negedge resetn) begin if (!resetn) q <= 36'H000000000; else q <= d; end assign d[35:0] = {q[35]^q[24]^znor,q[35:1]}; assign lout[35:0] = q[35:0]; assign znor1 = ~|q[23:0]; assign znor2 = ~|q[34:24]; assign znor = znor1&znor2; endmodule

64

`timescale 1ns / 1ps //////////////////////////////////////////////////////////////////////////////// // Company: // Engineer: // // Create Date: 13:29:29 11/01/05 // Design Name: // Module Name: lfsr36top // Project Name: // Target Device: // Tool versions: // Description: // // Dependencies: // // Revision: // Revision 0.01 - File Created // Additional Comments: // //////////////////////////////////////////////////////////////////////////////// module modpatt_v; // Inputs reg Clk; reg Reset; reg TE; // Outputs wire PA; wire PB; wire PC; wire [3:0] Chan; // Instantiate the Unit Under Test (UUT) main uut (

65

.PA(PA), .PB(PB), .PC(PC), .Chan(Chan), .Clk(Clk), .Reset(Reset), .TE(TE) ); initial begin // Initialize Inputs Clk = 0; Reset = 0; TE = 0; // Wait 100 ns for global reset to finish #100; // Add stimulus here Reset = 1; TE = 1; end //Clock is 16.7MHZ (60ns), simulate in modelsim for 6us for the VCD file always #30 Clk = ~ Clk; initial begin $dumpfile ("mod.vcd"); $dumpvars(1, modpatt_v.uut);

66

end endmodule `

67

APPENDIX C

XILINX REPORTS

TABLE OF CONTENTS

1) Synthesis Options Summary

2) HDL Compilation

3) HDL Analysis

4) HDL Synthesis

5) Advanced HDL Synthesis

5.1) HDL Synthesis Report

6) Low Level Synthesis

7) Final Report

7.1) Device utilization summary

* Synthesis Options Summary *

---- Source Parameters

Input File Name : "top.prj"

Input Format : mixed

Ignore Synthesis Constraint File : NO

---- Target Parameters

68

Output File Name : "top"

Output Format : NGC

Target Device : xc2s200-6-pq208

---- Source Options

Top Module Name : top

Automatic FSM Extraction : YES

FSM Encoding Algorithm : Auto

FSM Style : lut

RAM Extraction : Yes

RAM Style : Auto

ROM Extraction : Yes

ROM Style : Auto

Mux Extraction : YES

Mux Style : Auto

Decoder Extraction : YES

Priority Encoder Extraction : YES

Shift Register Extraction : YES

Logical Shifter Extraction : YES

XOR Collapsing : YES

69

Resource Sharing : YES

Multiplier Style : lut

Automatic Register Balancing : No

---- Target Options

Add IO Buffers : YES

Global Maximum Fanout : 100

Add Generic Clock Buffer(BUFG) : 4

Register Duplication : YES

Equivalent register Removal : YES

Slice Packing : YES

Pack IO Registers into IOBs : auto

---- General Options

Optimization Goal : Speed

Optimization Effort : 1

Keep Hierarchy : NO

Global Optimization : AllClockNets

RTL Output : Yes

70

Write Timing Constraints : NO

Hierarchy Separator : /

Bus Delimiter : <>

Case Specifier : maintain

Slice Utilization Ratio : 100

Slice Utilization Ratio Delta : 5

---- Other Options

lso : top.lso

Read Cores : YES

cross_clock_analysis : NO

verilog2001 : YES

safe_implementation : No

Optimize Instantiated Primitives : NO

tristate2logic : Yes

use_clock_enable : Yes

use_sync_set : Yes

use_sync_reset : Yes

enable_auto_floorplanning : No

71

======================================================

===================

* HDL Compilation *

Compiling verilog file "lfsr_fsm.v"

Module <lfsr_fsm> compiled

Compiling verilog file "lfsr_andor_mux.v"

Module <lfsr_andor_mux> compiled

Compiling verilog file "top.v"

Module <top> compiled

No errors in compilation

Analysis of file <"top.prj"> succeeded.

* HDL Analysis *

Analyzing top module <top>.

Module <top> is correct for synthesis.

Set property "resynthesize = true" for unit <top>.

Analyzing module <lfsr_fsm>.

72

Module <lfsr_fsm> is correct for synthesis.

Analyzing module <lfsr_andor_mux>.

Module <lfsr_andor_mux> is correct for synthesis.

* HDL Synthesis *

Synthesizing Unit <lfsr_andor_mux>.

Related source file is "lfsr_andor_mux.v".

Unit <lfsr_andor_mux> synthesized.

Synthesizing Unit <lfsr_fsm>.

Related source file is "lfsr_fsm.v".

Found 1-bit register for signal <en1>.

Found 1-bit register for signal <en2>.

Found 1-bit register for signal <sel1>.

Found 1-bit register for signal <sel2>.

Found 3-bit comparator greatequal for signal <$n0000> created at line 54.

73

Found 3-bit up counter for signal <count>.

Summary:

inferred 1 Counter(s).

inferred 4 D-type flip-flop(s).

inferred 1 Comparator(s).

Unit <lfsr_fsm> synthesized.

Synthesizing Unit <top>.

Related source file is "top.v".

WARNING:Xst:1780 - Signal <anor> is never used or assigned.

Found 1-bit xor2 for signal <$n0000> created at line 92.

Found 4-bit register for signal <q_lower>.

Found 1-bit register for signal <q_mid>.

Found 4-bit register for signal <q_upper>.

Summary:

inferred 1 D-type flip-flop(s).

Unit <top> synthesized.

* Advanced HDL Synthesis *

74

=================================================

Advanced RAM inference ...

Advanced multiplier inference ...

Advanced Registered AddSub inference ...

Dynamic shift register inference ...

HDL Synthesis Report

Macro Statistics

# Counters : 1

3-bit up counter : 1

# Registers : 7

1-bit register : 5

4-bit register : 2

# Comparators : 1

3-bit comparator greatequal : 1

# Xors : 1

1-bit xor2 : 1

75

* Low Level Synthesis *

Optimizing unit <top> ...

Optimizing unit <lfsr_fsm> ...

Optimizing unit <lfsr_andor_mux> ...

Loading device for application Rf_Device from file 'v200.nph' in

environment C:/Xilinx.

Mapping all equations...

Building and optimizing final netlist ...

Found area constraint ratio of 100 (+ 5) on block top, actual ratio is 0.

* Final Report *

Final Results

RTL Top Level Output File Name : top.ngr

Top Level Output File Name : top

Output Format : NGC

Optimization Goal : Speed

Keep Hierarchy : NO

76

Design Statistics

# IOs : 11

Macro Statistics :

# Registers : 17

# 1-bit register : 17

# Comparators : 1

# 3-bit comparator greatequal : 1

Cell Usage :

# BELS : 16

# INV : 1

# LUT2_L : 2

# LUT3 : 1

# LUT3_L : 5

# LUT4 : 6

# LUT4_L : 1

# FlipFlops/Latches : 16

# FDC : 4

# FDE : 4

# FDP : 5

77

# FDR : 2

# FDS : 1

# Clock Buffers : 1

# BUFGP : 1

# IO Buffers : 10

# IBUF : 2

# OBUF : 8

Device utilization summary:

---------------------------

Selected Device : 2s200pq208-6

Number of Slices: 9 out of 2352 0%

Number of Slice Flip Flops: 16 out of 4704 0%

Number of 4 input LUTs: 15 out of 4704 0%

Number of bonded IOBs: 11 out of 144 7%

Number of GCLKs: 1 out of 4 25%

78

Total memory usage is 86756 kilobytes

Number of errors : 0 ( 0 filtered)

Number of warnings : 1 ( 0 filtered)

Number of infos : 1 ( 0 filtered)

Release 7.1.02i - XPower SoftwareVersion:H.40 Copyright (c) 1995-2005 Xilinx, Inc. All rights reserved. Design: main.ncd Preferences: main.pcf VCD File: C:\Xilinx\bin\Design with inputs from low power lfsr\mod.vcd Part: 2s200pq208-6 Data version: PRELIMINARY,v1.0,07-31-02 XPower and Datasheet may have some Quiescent Current differences. This is due to the fact that the quiescent numbers in XPower are based on measurements of real designs with active functional elements reflecting real world design scenarios. Power summary: I(mA) P(mW) ---------------------------------------------------------------- Total estimated power consumption: 10 --- Vccint 2.50V: 1 2 Vcco33 3.30V: 2 8 --- Clocks: 0 0 Inputs: 1 2 Logic: 0 1 Outputs:

79

Vcco33 0 1 Signals: 0 0 --- Quiescent Vcco33 3.30V: 2 7 Startup Vccint 2.5V: 500 --- Package power limits, ambient 25C: 1935 250 LFM: 2620 500 LFM: 2970 750 LFM: 3209 Thermal summary: ---------------------------------------------------------------- Estimated junction temperature: 25C 250 LFM 25C 500 LFM 25C 750 LFM 25C Ambient temp: 25C Case temp: 25C Theta J-A range: 31 - 33C/W --- Max ambient at junction max of 85C: 85C 250 LFM 85C 500 LFM 85C 750 LFM 85C Decoupling Network Summary: Cap Range (uF) # ---------------------------------------------------------------- Capacitor Recommendations: Total for Vccint : 12 470.0 - 1000.0 : 1 0.470 - 2.200 : 1 0.0470 - 0.2200 : 2 0.0100 - 0.0470 : 3 0.0010 - 0.0047 : 5 --- Invalid Program Mode

80

Total for Vcco33 : 8 470.0 - 1000.0 : 1 0.0470 - 0.2200 : 1 0.0100 - 0.0470 : 2 0.0010 - 0.0047 : 4 Power details: ------------------------------------------------------------------------------- Inputs: Loads Loading(fF) C(pF) F(MHz) I(mA) P(mW) ------------------------------------------------------------------------------- Clk_BUFGP/IBUFG 16000 16.7 0.7 1.7 Reset_IBUF 2970 0.1 0.0 0.0 TE_IBUF 2970 0.1 0.0 0.0 ------------------------------------------------------------------------------- Outputs:1 Loads Loading(fF) C(pF) F(MHz) I(mA) P(mW) ------------------------------------------------------------------------------- Vcco33 PC_OBUF 35000 13 0.7 0.1 0.3 Chan_0_OBUF 35000 13 0.3 0.0 0.1 Chan_2_OBUF 35000 13 0.3 0.0 0.1 PB_OBUF 35000 13 0.3 0.0 0.1 Chan_1_OBUF 35000 13 0.2 0.0 0.1 Chan_3_OBUF 35000 13 0.1 0.0 0.0 PA_OBUF 35000 13 0.1 0.0 0.0 ------------------------------------------------------------------------------- Logic: Loads Loading(fF) C(pF) F(MHz) I(mA) P(mW) ------------------------------------------------------------------------------- sr2/_n00631 2400 0.9 0.0 0.0 sr2/_n00661 2400 0.9 0.0 0.0 M3/PC384_SW1_SW0 2400 0.8 0.0 0.0 M3/PC622_SW0 2400 0.8 0.0 0.0 sr2/_n00841 2400 0.8 0.0 0.0 sr2/_n00871 2400 0.8 0.0 0.0 sr2/_n00901 2400 0.8 0.0 0.0 M3/PC104 2400 0.7 0.0 0.0 M3/PC252_SW0 2400 0.7 0.0 0.0 M3/PC252_SW1 2400 0.7 0.0 0.0

81

M3/PC634 2400 0.7 0.0 0.0 sr2/_n00691 2400 0.7 0.0 0.0 sr2/_n00721 2400 0.7 0.0 0.0 sr2/_n00751 2400 0.7 0.0 0.0 sr2/_n00781 2400 0.7 0.0 0.0 sr2/_n00811 2400 0.7 0.0 0.0 sr2/_n00931 2400 0.7 0.0 0.0 sr2/_n00961 2400 0.7 0.0 0.0 sr2/_n00991 2400 0.7 0.0 0.0 M4/I<7>1 2400 0.7 0.0 0.0 M4/I<6>1 2400 0.6 0.0 0.0 M4/I<5>1 2400 0.6 0.0 0.0 M4/I<0>1 2400 0.6 0.0 0.0 M4/I<0>2 2400 0.6 0.0 0.0 M4/I<4>1 2400 0.6 0.0 0.0 M4/I<3>1 2400 0.5 0.0 0.0 M4/I<3>2 2400 0.5 0.0 0.0 M4/I<2>1 2400 0.5 0.0 0.0 M4/I<2>2 2400 0.5 0.0 0.0 M3/PC104_SW1 2400 0.5 0.0 0.0 M4/I<1>1 2400 0.5 0.0 0.0 M4/I<1>2 2400 0.5 0.0 0.0 M2/PB88 2400 0.4 0.0 0.0 M2/PB92 2400 0.4 0.0 0.0 M2/PB99 2400 0.4 0.0 0.0 sr2/_n00071 2400 0.4 0.0 0.0 sr2/_n00101 2400 0.4 0.0 0.0 sr2/_n00131 2400 0.4 0.0 0.0 sr2/_n01021 2400 0.4 0.0 0.0 sr2/_n01051 2400 0.4 0.0 0.0 sr2/_n01081 2400 0.4 0.0 0.0 sr2/_n01111 2400 0.4 0.0 0.0 M4/I<6>2 2400 0.3 0.0 0.0 M4/I<8>2 2400 0.3 0.0 0.0 sr2/_n00161 2400 0.3 0.0 0.0 sr2/_n00191 2400 0.3 0.0 0.0 sr2/_n00221 2400 0.3 0.0 0.0

82

M4/I<8>1 2400 0.3 0.0 0.0 M1/PA66 2400 0.3 0.0 0.0 M1/Mxor_X1_Result<6>1 2400 0.3 0.0 0.0 M1/Mxor_X1_Result<7>1 2400 0.3 0.0 0.0 M2/PB122 2400 0.3 0.0 0.0 M4/I<4>2 2400 0.3 0.0 0.0 M4/I<5>2 2400 0.3 0.0 0.0 M5/_n0008 2400 0.3 0.0 0.0 M5/_n0008_SW0 2400 0.3 0.0 0.0 M5/_n0009_SW0 2400 0.3 0.0 0.0 M5/_n00101 2400 0.3 0.0 0.0 M3/PC622 2400 0.2 0.0 0.0 M2/PB122_SW0 2400 0.2 0.0 0.0 M3/PC454 2400 0.2 0.0 0.0 M3/PC384 2400 0.2 0.0 0.0 M3/PC384_SW1 2400 0.2 0.0 0.0 M1/PA66_SW0 2400 0.2 0.0 0.0 M1/Mxor_X1_Result<4>1 2400 0.2 0.0 0.0 M1/Mxor_X1_Result<5>1 2400 0.2 0.0 0.0 M4/I<7>2 2400 0.2 0.0 0.0 M5/_n0009 2400 0.2 0.0 0.0 sr2/_n00251 2400 0.2 0.0 0.0 sr2/_n00601 2400 0.2 0.0 0.0 M3/PC591_SW0 2400 0.1 0.0 0.0 M1/PA57 2400 0.1 0.0 0.0 M2/PB67 2400 0.1 0.0 0.0 M2/PB67_SW0 2400 0.1 0.0 0.0 M2/PB34 2400 0.1 0.0 0.0 M1/PA21 2400 0.1 0.0 0.0 M2/PB30 2400 0.1 0.0 0.0 M1/Mxor_X1_Result<0>1 2400 0.1 0.0 0.0 M1/Mxor_X1_Result<1>1 2400 0.1 0.0 0.0 M1/Mxor_X1_Result<2>1 2400 0.1 0.0 0.0 M1/PA81 2400 0.1 0.0 0.0 M3/PC252 2400 0.1 0.0 0.0 M5/_n001138 2400 0.1 0.0 0.0 sr2/_n00281 2400 0.1 0.0 0.0

83

sr2/_n00311 2400 0.1 0.0 0.0 sr2/_n00341 2400 0.1 0.0 0.0 sr2/_n00371 2400 0.1 0.0 0.0 sr2/_n00401 2400 0.1 0.0 0.0 sr2/_n00431 2400 0.1 0.0 0.0 sr2/_n00461 2400 0.1 0.0 0.0 sr2/lfsr_fsm_a/count__n0001<0>1 2400 0.1 0.0 0.0 sr2/lfsr_fsm_a/count__n0001<1>1 2400 0.1 0.0 0.0 sr2/lfsr_fsm_a/count__n0001<2>1 2400 0.1 0.0 0.0 M1/PA10 2400 0.1 0.0 0.0 M3/PC591_SW1 2400 0.1 0.0 0.0 M3/PC606 2400 0.0 0.0 0.0 M3/PC268_SW0 2400 0.0 0.0 0.0 M2/PB11 2400 0.0 0.0 0.0 M3/PC591 2400 0.0 0.0 0.0 M3/PC268 2400 0.0 0.0 0.0 Clk_BUFGP/BUFG.CE_POWER 0 0.0 0.0 0.0 M5/_n001112 2400 0.0 0.0 0.0 sr2/Mxor__n0000_Result1 2400 0.0 0.0 0.0 sr2/_n00491 2400 0.0 0.0 0.0 sr2/_n00521 2400 0.0 0.0 0.0 sr2/_n00551 2400 0.0 0.0 0.0 sr2/lfsr_fsm_a/_n00011 2400 0.0 0.0 0.0 sr2/lfsr_fsm_a/_n00021 2400 0.0 0.0 0.0 sr2/lfsr_fsm_a/_n00031 2400 0.0 0.0 0.0 sr2/lfsr_fsm_a/_n00041 2400 0.0 0.0 0.0 sr2/lfsr_fsm_a/count_0 275 0.0 0.0 0.0 sr2/lfsr_fsm_a/count_1 275 0.0 0.0 0.0 sr2/lfsr_fsm_a/count_2 275 0.0 0.0 0.0 sr2/lfsr_fsm_a/en1 275 0.0 0.0 0.0 sr2/lfsr_fsm_a/en2 275 0.0 0.0 0.0 sr2/lfsr_fsm_a/sel1 275 0.0 0.0 0.0 sr2/lfsr_fsm_a/sel2 275 0.0 0.0 0.0 sr2/q_lower_0 275 0.0 0.0 0.0 sr2/q_lower_1 275 0.0 0.0 0.0 sr2/q_lower_10 275 0.0 0.0 0.0 sr2/q_lower_11 275 0.0 0.0 0.0

84

sr2/q_lower_12 275 0.0 0.0 0.0 sr2/q_lower_13 275 0.0 0.0 0.0 sr2/q_lower_14 275 0.0 0.0 0.0 sr2/q_lower_15 275 0.0 0.0 0.0 sr2/q_lower_16 275 0.0 0.0 0.0 sr2/q_lower_17 275 0.0 0.0 0.0 sr2/q_lower_2 275 0.0 0.0 0.0 sr2/q_lower_3 275 0.0 0.0 0.0 sr2/q_lower_4 275 0.0 0.0 0.0 sr2/q_lower_5 275 0.0 0.0 0.0 sr2/q_lower_6 275 0.0 0.0 0.0 sr2/q_lower_7 275 0.0 0.0 0.0 sr2/q_lower_8 275 0.0 0.0 0.0 sr2/q_lower_9 275 0.0 0.0 0.0 sr2/q_mid 275 0.0 0.0 0.0 sr2/q_upper_0 275 0.0 0.0 0.0 sr2/q_upper_1 275 0.0 0.0 0.0 sr2/q_upper_10 275 0.0 0.0 0.0 sr2/q_upper_11 275 0.0 0.0 0.0 sr2/q_upper_12 275 0.0 0.0 0.0 sr2/q_upper_13 275 0.0 0.0 0.0 sr2/q_upper_14 275 0.0 0.0 0.0 sr2/q_upper_15 275 0.0 0.0 0.0 sr2/q_upper_16 275 0.0 0.0 0.0 sr2/q_upper_16.BY0 0 0.0 0.0 0.0 sr2/q_upper_17 275 0.0 0.0 0.0 sr2/q_upper_2 275 0.0 0.0 0.0 sr2/q_upper_3 275 0.0 0.0 0.0 sr2/q_upper_4 275 0.0 0.0 0.0 sr2/q_upper_5 275 0.0 0.0 0.0 sr2/q_upper_6 275 0.0 0.0 0.0 sr2/q_upper_7 275 0.0 0.0 0.0 sr2/q_upper_8 275 0.0 0.0 0.0 sr2/q_upper_9 275 0.0 0.0 0.0 ------------------------------------------------------------------------------- Signals: Loads Loading(fF) C(pF) F(MHz) I(mA) P(mW) -------------------------------------------------------------------------------

85

PC_OBUF 0 4 0.7 0.0 ~0.0 PB_OBUF 0 8 0.3 0.0 ~0.0 Reset_IBUF 0 14 0.1 0.0 0.0 srBus<24> 0 1 0.7 0.0 ~0.0 srBus<22> 0 1 0.7 0.0 ~0.0 srBus<20> 0 1 0.4 0.0 ~0.0 PA_OBUF 0 8 0.1 0.0 0.0 srBus<34> 0 0 0.9 0.0 ~0.0 srBus<12> 0 1 0.3 0.0 ~0.0 srBus<14> 0 1 0.3 0.0 ~0.0 srBus<17> 0 1 0.4 0.0 ~0.0 srBus<13> 0 1 0.3 0.0 ~0.0 srBus<16> 0 1 0.4 0.0 ~0.0 srBus<33> 0 0 0.9 0.0 ~0.0 srBus<30> 0 0 0.7 0.0 ~0.0 srBus<18> 0 0 0.4 0.0 ~0.0 srBus<25> 0 0 0.8 0.0 ~0.0 Chan_0_OBUF 0 1 0.3 0.0 ~0.0 N573 0 0 0.8 0.0 ~0.0 srBus<15> 0 0 0.4 0.0 ~0.0 Chan_1_OBUF 0 1 0.2 0.0 ~0.0 I<8> 0 0 0.3 0.0 ~0.0 I<4> 0 1 0.3 0.0 ~0.0 srBus<19> 0 0 0.4 0.0 ~0.0 Chan_2_OBUF 0 1 0.3 0.0 ~0.0 I<7> 0 1 0.2 0.0 ~0.0 X1<4> 0 1 0.2 0.0 ~0.0 I<5> 0 0 0.3 0.0 ~0.0 I<6> 0 0 0.3 0.0 ~0.0 srBus<5> 0 2 0.1 0.0 0.0 srBus<21> 0 0 0.4 0.0 ~0.0 srBus<11> 0 1 0.2 0.0 ~0.0 X1<6> 0 0 0.3 0.0 ~0.0 srBus<10> 0 1 0.1 0.0 0.0 X1<0> 0 1 0.1 0.0 0.0 srBus<28> 0 0 0.7 0.0 ~0.0 srBus<4> 0 1 0.1 0.0 0.0

86

M4/N4 0 0 0.5 0.0 ~0.0 srBus<7> 0 1 0.1 0.0 0.0 srBus<6> 0 1 0.1 0.0 0.0 srBus<9> 0 1 0.1 0.0 0.0 X1<2> 0 1 0.1 0.0 0.0 srBus<8> 0 1 0.1 0.0 0.0 CHOICE932 0 0 0.2 0.0 ~0.0 CHOICE788 0 1 0.1 0.0 ~0.0 Chan_3_OBUF 0 1 0.1 0.0 0.0 X1<7> 0 0 0.3 0.0 ~0.0 X1<1> 0 1 0.1 0.0 0.0 N555 0 0 0.2 0.0 ~0.0 CHOICE783 0 1 0.1 0.0 0.0 X1<5> 0 0 0.2 0.0 ~0.0 srBus<35> 0 0 0.2 0.0 ~0.0 CHOICE801 0 0 0.1 0.0 ~0.0 N559 0 0 0.1 0.0 ~0.0 CHOICE817 0 0 0.1 0.0 0.0 CHOICE818 0 0 0.1 0.0 ~0.0 N569 0 0 0.0 0.0 0.0 CHOICE980 0 0 0.0 0.0 0.0 CHOICE810 0 0 0.0 0.0 0.0 N567 0 0 0.1 0.0 0.0 CHOICE902 0 0 0.0 0.0 0.0 CHOICE769 0 0 0.0 0.0 0.0 CHOICE803 0 0 0.3 0.0 ~0.0 CHOICE826 0 0 0.1 0.0 ~0.0 CHOICE835 0 0 0.0 0.0 0.0 CHOICE836 0 0 0.0 0.0 0.0 CHOICE837 0 0 0.0 0.0 0.0 CHOICE869 0 0 0.0 0.0 0.0 CHOICE901 0 0 0.0 0.0 0.0 CHOICE945 0 0 0.2 0.0 ~0.0 CHOICE979 0 0 0.0 0.0 0.0 CHOICE981 0 0 0.2 0.0 ~0.0 I<0> 0 0 0.0 0.0 0.0 I<1> 0 0 0.0 0.0 0.0

87

I<2> 0 1 0.0 0.0 0.0 I<3> 0 1 0.0 0.0 0.0 M4/N0 0 0 0.3 0.0 ~0.0 M4/N10 0 0 0.5 0.0 ~0.0 M4/N12 0 0 0.6 0.0 ~0.0 M4/N14 0 0 0.7 0.0 ~0.0 M4/N16 0 0 0.6 0.0 ~0.0 M4/N2 0 0 0.6 0.0 ~0.0 M4/N6 0 0 0.5 0.0 ~0.0 M4/N8 0 0 0.6 0.0 ~0.0 N11 0 0 0.0 0.0 0.0 N547 0 0 0.1 0.0 ~0.0 N549 0 0 0.0 0.0 0.0 N557 0 0 0.2 0.0 ~0.0 N561 0 0 0.0 0.0 0.0 N563 0 0 0.0 0.0 0.0 N565 0 0 0.5 0.0 ~0.0 N571 0 0 0.2 0.0 ~0.0 N9 0 0 0.0 0.0 0.0 sr2/d<35> 0 0 0.0 0.0 0.0 sr2/lfsr_fsm_a/count<0> 0 2 0.0 0.0 0.0 sr2/lfsr_fsm_a/count<1> 0 2 0.0 0.0 0.0 sr2/lfsr_fsm_a/count<2> 0 3 0.0 0.0 0.0 sr2/lfsr_fsm_a/en1 0 9 0.0 0.0 0.0 sr2/lfsr_fsm_a/en2 0 9 0.0 0.0 0.0 sr2/lfsr_fsm_a/sel1 0 6 0.0 0.0 0.0 sr2/lfsr_fsm_a/sel2 0 6 0.0 0.0 0.0 sr2/q_lower<0> 0 12 0.0 0.0 0.0 sr2/q_lower<10> 0 1 0.0 0.0 0.0 sr2/q_lower<11> 0 1 0.0 0.0 0.0 sr2/q_lower<12> 0 1 0.0 0.0 0.0 sr2/q_lower<13> 0 1 0.0 0.0 0.0 sr2/q_lower<14> 0 1 0.0 0.0 0.0 sr2/q_lower<15> 0 1 0.0 0.0 0.0 sr2/q_lower<16> 0 1 0.0 0.0 0.0 sr2/q_lower<17> 0 1 0.0 0.0 0.0 sr2/q_lower<1> 0 1 0.0 0.0 0.0

88

sr2/q_lower<2> 0 1 0.0 0.0 0.0 sr2/q_lower<3> 0 1 0.0 0.0 0.0 sr2/q_lower<4> 0 2 0.0 0.0 0.0 sr2/q_lower<5> 0 1 0.0 0.0 0.0 sr2/q_lower<6> 0 1 0.0 0.0 0.0 sr2/q_lower<7> 0 1 0.0 0.0 0.0 sr2/q_lower<8> 0 1 0.0 0.0 0.0 sr2/q_lower<9> 0 1 0.0 0.0 0.0 sr2/q_mid 0 1 0.0 0.0 0.0 sr2/q_upper_0 0 1 0.0 0.0 0.0 sr2/q_upper_1 0 1 0.0 0.0 0.0 sr2/q_upper_10 0 1 0.0 0.0 0.0 sr2/q_upper_11 0 1 0.0 0.0 0.0 sr2/q_upper_12 0 1 0.0 0.0 0.0 sr2/q_upper_13 0 1 0.0 0.0 0.0 sr2/q_upper_14 0 2 0.0 0.0 0.0 sr2/q_upper_15 0 1 0.0 0.0 0.0 sr2/q_upper_16 0 1 0.0 0.0 0.0 sr2/q_upper_17 0 2 0.0 0.0 0.0 sr2/q_upper_2 0 1 0.0 0.0 0.0 sr2/q_upper_3 0 1 0.0 0.0 0.0 sr2/q_upper_4 0 1 0.0 0.0 0.0 sr2/q_upper_5 0 1 0.0 0.0 0.0 sr2/q_upper_6 0 2 0.0 0.0 0.0 sr2/q_upper_7 0 1 0.0 0.0 0.0 sr2/q_upper_8 0 1 0.0 0.0 0.0 sr2/q_upper_9 0 1 0.0 0.0 0.0 srBus<1> 0 2 0.0 0.0 0.0 srBus<23> 0 0 0.7 0.0 ~0.0 srBus<26> 0 0 0.8 0.0 ~0.0 srBus<27> 0 0 0.8 0.0 ~0.0 srBus<29> 0 0 0.7 0.0 ~0.0 srBus<2> 0 1 0.0 0.0 0.0 srBus<31> 0 0 0.7 0.0 ~0.0 srBus<32> 0 0 0.7 0.0 ~0.0 srBus<3> 0 2 0.0 0.0 0.0 -------------------------------------------------------------------------------

89

Clocks:2 Loads Loading(fF) C(pF) F(MHz) I(mA) P(mW) ------------------------------------------------------------------------------- TE_IBUF TE_IBUF 0 2 0.1 0.0 0.0 Clk_BUFGP/IBUFG Logic: Clk_BUFGP/BUFG 80 0.0 0.0 0.0 Nets: Clk_BUFGP 0 3 0.0 0.0 0.0 Clk_BUFGP/IBUFG 0 0 0.0 0.0 0.0 ------------------------------------------------------------------------------- Power improvement guide: ------------------------------------------------------------------------------- For further suggestions on power improvements see application note no. 421 Analysis completed: Fri Dec 09 15:54:22 2005

90

APPENDIX D

C432 VERILOG

module TopLevel432b (E, A, B, C, PA, PB, PC, Chan);

input[8:0] E, A, B, C;

output PA, PB, PC;

output[3:0] Chan;

wire[8:0] X1, X2, I;

PriorityA M1(E, A, PA, X1);

PriorityB M2(E, X1, B, PB, X2);

PriorityC M3(E, X1, X2, C, PC);

EncodeChan M4(E, A, B, C, PA, PB, PC, I);

DecodeChan M5(I, Chan);

endmodule /* TopLevel432b */

module PriorityA(E, A, PA, X1);

input[8:0] E, A;

output PA;

output[8:0] X1;

wire [8:0] Ab, EAb;

91

assign Ab = ~A;

assign EAb = ~(Ab & E);

assign PA = ~&EAb;

assign X1 = EAb ^ {9{PA}};

endmodule /* PriorityA */

module PriorityB(E, X1, B, PB, X2);

input[8:0] E, X1, B;

output PB;

output[8:0] X2;

wire [8:0] Eb, EbB, XEB;

assign Eb = ~E;

assign EbB = ~(Eb | B);

assign XEB = ~(X1 & EbB);

assign PB = ~&XEB;

assign X2 = XEB ^ {9{PB}};

endmodule /* PriorityB */

module PriorityC(E, X1, X2, C, PC);

input[8:0] E, X1, X2, C;

output PC;

92

wire [8:0] Eb, EbC, XEC;

assign Eb = ~E;

assign EbC = ~(Eb | C);

assign XEC = ~(X1 & X2 & EbC);

assign PC = ~&XEC;

endmodule /*PriorityC */

module EncodeChan(E, A, B, C, PA, PB, PC, I);

input[8:0] E, A, B, C;

input PA, PB, PC;

output[8:0] I;

wire [8:0] APA, BPB, CPC;

assign APA = ~(A & {9{PA}});

assign BPB = ~(B & {9{PB}});

assign CPC = ~(C & {9{PC}});

assign I = ~(E & APA & BPB & CPC);

endmodule /* EncodeChan */

module DecodeChan(I, Chan);

input[8:0] I;

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output[3:0] Chan;

wire Iand, I8b, I1b, I2b, I3b, I5b, I56, I245, I3456, I1256;

assign I8b = ~I[8];

assign Iand = &I[7:0];

assign Chan[3] = ~(I8b | Iand);

assign I1b = ~I[1];

assign I2b = ~I[2];

assign I3b = ~I[3];

assign I5b = ~I[5];

assign I56 = ~(I5b & I[6]);

assign I245 = ~(I2b & I[4] & I[5]);

assign I3456 = ~(I3b & I[4] & I[5] & I[6]);

assign I1256 = ~(I1b & I[2] & I[5] & I[6]);

assign Chan[2] = ~(I[4] & I[6] & I[7] & I56);

assign Chan[1] = ~(I[6] & I[7] & I245 & I3456);

assign Chan[0] = ~(I[7] & I56 & I1256 & I3456);

endmodule /* DecodeChan */

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Agree (Permission is granted.)

________Aftab Farooqi______________________________ __04-29-06_______ Student Signature Date Disagree (Permission is not granted.) _______________________________________________ _________________ Student Signature Date