SAP 3 ARCHITECTURE

7/23/2019 SAP 3 ARCHITECTURE

1/5CENG03. COMPUTERSYSTEM ARCHITECTURE. SAP 3. esquiv

AP 3

P3 instruction set includes all the SAP 2 instructionss new instructions.

SAP 3 Programming Model

ote: The additional CPU registers, D, E, H and L areused for more efficient data processing.

The F register stores flag bits: S (sign flag), Z

(zero flag) and others.

ADVANTAGE OF MORE CPU REGISTERS

1. Programs can run faster2. Simplifies program writing

ARITHMETIC INSTRUCTIONS

ote: CY = CARRY if operation is ADDCY = CARRY if operation is SUB

ote: The 8-bit sum S7S0 is stored in theaccumulator. The CY is stored in a special FFcalled CARRY FLAG.

ote: The CY flag acts like the next higher bit of theaccumulator, i.e. CY = AB

CARRY FLAG INSTRUCTIONS

Note: There are two instructions that can be used control the carry flag.

1. STC - SET CARRY-will set the CY flag if it is not sete.g. if CY=0, STC produces CY=1

2. CMC - COMPLEMENT THE CARRY- complements the value of CY

ADD INSTRUCTIONS

ADD REG

Example 1:

A = 1111 0001

E = 0000 1000

Solution:

1111 0001+ 0000 1000

1111 10001

Answer:

Example 2:

A = 1111 1111

L = 0000 0001

Solution:

1111 1111+ 0000 00011 0000 0000

Answer:

A

FC B C

SL D E F

H L

CY A7 A6 A5 A2 A1 A0

CY=0 A=1111 1001

CY= 1 A=0000 0000



ADC INSTRUCTIONS(ADC = Add with carry)

ADD REG

ample 1:

A = 1000 0011

E = 0001 0010CY = 1

lution:

1000 0011+ 0001 0010

11001 0110

swer:

SUB INSTRUCTIONS

SUB REG

ample 1:

A = 0000 1111

C = 0000 0001

lution:

0000 1111- 0000 0001

0000 1110

swer:

Example 2:

A = 0000 1100

C = 0001 0010

Solution:

0000 1100

- 0001 00101 1111 1010

Answer:

SBB INSTRUCTIONS(SBB = Subtract with borrow)

Note: It subtracts the contents of a specified registand the CY flag from the accumulator contents.

Example 1:

A = 1111 1111

E = 0000 0010

CY = 1

Solution:

1111 1111- 0000 0010

11111 1100

Answer:

CY=0 A=1001 0110

CY=0 A=0000 1110

CY=1 A=1111 1010

CY=0 A=1111 1100



INCREMENTS

INR REG

ote: The INR instruction has no effect on the carryg, but it does affect the sign flags and zero flags.

ample 1:

B = 1111 1111, and

The initial flags are

S=1, Z=0, CY=0

swer:

DECREMENTS

DEC REG

ample 1:

E = 0000 0000

S=0, Z=1, CY=0

swer:

ROTATE ALL LEFT (RAL)

Note: The CY flag is included in the rotation of bits

Example 1:

CY = 1

A = 0111 0100

Answer:

ROTATE ALL RIGHT (RAR)

Note: The CY flag is included in the rotation of bits

Example 1:

CY = 1

A = 0111 0100

Answer:

B = 0000 0000S=0, Z=1, CY=0

E = 1111 1111S=1, Z=0, CY=0

CY=0A = 1110 1001

CY MSB A LSB

CY=0A = 1011 1010

CY MSB A LSB



ROTATE LEFT WITH CARRY (RLC)

ote: This instruction will rotate the contents of thecumulator to the left and the MSB is saved in the CYg.

ample 1:

CY = 1

A = 0111 0100

swer:

ROTATE RIGHT WITH CARRY (RRC)

ote: The LSB is saved in the CY flag.

ample 1:

CY = 1A = 0111 0100

swer:

MULTIPLY AND DIVIDE BY 2

Uses of rotate instructions:

1. Parallel to serial and serial to parallel converof data.

2. Has the effect of multiplying or dividing theaccumulator contents by a factor of 2.

Note: With the carry flag reset, a RAL has the effecmultiplying by 2, while the RAR divides by 2.

Example 1:

RAL

CY = 0

A = 0000 0111

Answer:

Example 2:

RAL

CY = 0

A = 0010 0001

Answer:

CY=0A = 1110 1000

CY MSB A LSB

CY=0A = 0011 1010

CY MSB A LSB

CY=0A = 0000 1110

CY=0A = 0100 0010


5/5CENG03 COMPUTERSYSTEM ARCHITECTURE SAP 3 esquiv

ample 3:

RAR

CY = 0

A = 0001 1000

swer:

ample 3:

RAR

CY = 0

A = 0000 1100

swer:

Example program:

Show a SAP 3 program that adds 700 and 400, withfinal answer stored in the H ad L registers.

INSTRUCTION

CY=0A = 0000 1100

CY=0A = 0000 0110

MVI A,

00H

MVI B,

02H

MVI C,

BCH

MVI D,

O3H

MVI E,

84H

ADD C

ADD E

MOV L, A

MVI A,

00H

ADC B

ADD D

MOV H, A

HLT

SAP 3 ARCHITECTURE

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