Branching Group Instructions (Part-III) - Return and Conditional return

RET:

This instruction transfers the program control from subroutine or subprogram to the main program.
It pops the address of the instruction next to CALL instruction in the main program from the stack and loads program counter with this address.
Then stack pointer is incremented by two.

No flags are affected.
It is a one byte instruction.
Register indirect addressing mode is used because the return address is available in the memory location pointed by stack pointer.

Example:

If SP = 2000H

RET ; This instruction will load program counter with 3000H and will transfer program control to 3000H.

Before execution:

After execution:

Rcond:

When the condition is true, this instruction transfers the program control from subprogram or subroutine to the main program.
It pops the address of the instruction next to CALL instruction from the stack and loads program counter with this address.
Then stack pointer is incremented by two.
When the condition is false, nothing happens.

No flags are affected. They are only checked.
It is a one byte instruction.
Register indirect addressing mode is used because the return address is available in the memory location pointed by stack pointer.

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Logical Group Instructions (Part-VI) - RLC, RRC, RAL, RAR

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Statement: Exchange the contents of memory locations 2000H and 2001H. Example: Initially, (2000H) = 34H (2001H) = 20H After exchanging, (2000H) = 20H (2001H) = 34H Program 1 using direct addressing instructions: LDA 2000H ; Get the contents of location 2000H into accumulator MOV B, A ; Move the contents of accumulator into register B LDA 2001H ; Get the contents of location 2001H into accumulator STA 2000H ; Store the contents of accumulator into location 2000H MOV A, B ; Move the contents of register B into accumulator STA 2001H ; Store the contents of accumulator into location 2001H HLT ...

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8085 Microprocessors Notes

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