What is an addressing mode Identify the addressing mode for

What is an addressing mode? Identify the addressing mode for each of the following instructions (both for the source and destination operands where it applies). MOV P1, #30H ADD A, #20 MOV R7, A MOV @R0, A INC DPTR ORL 20H, #30H CJNE A, 30H, NEXT DJNZ R4, BACK JMP @A+DPTR ACALL DELAY MOV 20H,00H MOV 00H, @R0 MOVC A, @A+DPTR MOVX A, @DPTR PUSH 20H SJMP FORWARD

Solution

Addressing mode is a way to address an operand. Operand means data on which we are going to operate or source data. It can be a direct address of memory, it can be register names, it can be any numerical data etc. e.g. MOV A,#6AH
In this example 6AH is operand. After execution of this instruction 6AH is added to the accumulator. We can execute this instruction by using 5 different ways. We can use 5 different addressing modes to execute this instruction. Following are the different type of addressing modes.

ü Immediate addressing mode

ü Direct addressing mode

ü Register addressing mode

ü Register indirect addressing mode

ü Indexed addressing mode.

MOV P1, #30H                Immediate

ADD A,#20                        Immediate

MOV R7, A                      Register

MOV @R0, A Indirect

INC DPTR Register

ORL 20H, #30H Immediate

CJNE A, 30H, NEXT INDIRECT

PUSH 20H DIRECT

MOV 20H, 0H   DIRECT

MOV 00H, @R0      REGISTER INDIRECT

MOVC A, @A+DPTR   INDEXED

MOVX A, @DPTR      REGISTER INDIRECT

SJMP FORWARD   RELATIVE         

DJNZ R4, BACK      RELATIVE

JUMP @A+DPTR   INDEXED