ECP2036 Microprocessor and Interfacing Registers Control & Status Registers Program Counter...

ECP2036 Microprocessor and Interfacing

Registers

Control & Status Registers

Program Counter

User-Visible Registers

Instruction Register

...

General-Purpose Reg.

Address Register

Data Register

Flag Register...


Program Counter




...


Address Register

Data Register

...

To hold the memory address of the next instruction to be executed

Default value at power on/reset:PC = 0000H or FFFFH (or other address

predetermined by the manufacturer)


Program Counter




...


Address Register

Data Register

Flag Register...

To hold the instruction fetched from external memory


Program Counter




...


Address Register

Data Register

Flag Register...

Can be assigned to a variety of functions by programmer


Program Counter




...


Address Register

Data Register

Flag Register...

To hold the address of next memory location to be addressed

Program Counter




...


Address Register

Data Register

Flag Register...

To hold the data fetched from memory




...


Address Register

Data Register

Flag Register...

Condition-code register that contains a number of flag bits.

Each flag bit is either set (“1”) or reset (“0”) by the result of an arithmetic or logical instruction that has just been executed

Memory

Memory Location-1

Memory Location-2Memory Address-1 Memory Address-2

Memory Location-nMemory Address-n

5 6 7 81 2 3 4

1 word = 8-bit data (for 8051)


Bus System (I)

Address Bus

These are the wires that carry the CPU generated address signals out to memory and to I/O devices.

The address signals only travel outwards from the CPU (unidirectional).

The number of address lines that a microprocessor has determines the size of the memory space that it can access.


Memory Size

No of Add. lines Size of memory space

8 28 = 256

16 216 = 65 536 = 64 K

20 220 = 1 048 576 = 1 M

24 224 = 16 777 216 = 16 M

32 232 = 4 294 967 296 = 4 G


Data Bus

These are the data signals that travel out of and into the P (bi-directional).

The number of wires in the data bus depends on the word size that the P operates with.

An 8-bit P will have a data bus consisting of 8 wires and a 32-bit P will have a data bus with 32 wires.

Bus System (II)


Control Bus

The control bus consists of wires, some of which carry signals from the CPU to external devices, while others carry signals from external devices to the CPU.

The number of wires present in the control bus varies from one P to another.

Examples of control bus signals are READ/, WAIT, READY, and HOLD.

Bus System (III)


von Neumann Architecture

Main Memory

ALU

CU

I/O


Basic Instruction Cycle

Execute Instruction

Start

Fetch Instruction

End

Fetch Cycle

Execute Cycle

PC = 0000H

PC = PC + n


Memory Read Operation - Step 1


CPU Memory

Address bus

Data bus

CPU places address (XXXX) of the memory location on the address bus

Memory request

Read

The CPU sends out the control signals Memory Request and Read to indicate that it wants to read from memory



CPU Memory

Address bus

Data bus

Memory request

Read

Accessed location at XXXX

Memory places data from the accessed location onto the data bus



CPU Memory

Address bus

Data bus

Memory request

Read

Memory request

Read

The CPU removes the Memory Request and Read signals

CPU latches the data into a register

Register

Memory Write Operation - Step 1


CPU Memory

Address bus

Data bus

CPU places address (YYYY) of the memory location on the address bus

The CPU sends out a Memory Request control signal to indicate that it wants to perform a memory operation

Memory request



CPU Memory

Address bus

Data bus

Memory request

CPU places the data from a register onto the data bus

Register

The CPU sends out a Write control signal to indicate that valid data is available on the data bus

Write



CPU Memory

Address bus

Data bus

Memory request

Memory copies the data bus into the accessed location

Register

Write

Accessed location at YYYY

The CPU removes the Write signal to complete the memory write operation

Memory request

Write

Assembly Language ProgramAn assembly language program is a program written using labels and mnemonics, in which each statement corresponds to a machine instruction.

; A test program

ORG 0000H MOV A, #01H

LOOP: RL AMOV P1, A ; output to port 1JMP LOOP

END


Assembling A Source Program

asm51program.src

program.obj

program.lst

An assembler is a program that translate an assembly language program into a machine language program.


Linking Object Files

RL51

program

program.m51

A linker/locator is a program that combines relocatable object programs (modules) and produces an absolute object program that is executable by a computer.

File3.objFile2.obj

File1.obj


BIN to HEX conversion

OH program.hexprogram.bin

Download to 8051


ECP2036 Microprocessor and Interfacing Registers Control & Status Registers Program Counter...

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