Instruction type MOV r, M in 8085 Microprocessor

Microprocessor8085

In 8085 Instruction set, MOV r, M is an instruction where the 8-bit data content of the memory location as pointed by HL register pair will be moved to the register r. Thus this is an instruction to load register r with the 8-bit value from a specified memory location whose 16-bit address is in HL register pair.

As r can have any of the seven values, there are seven opcodes for this type of instruction.

r = A, B, C, D, E, H, or L

Mnemonics, Operand Opcode Bytes
MOV A, M 7E 1
MOV B, M 46 1
MOV C, M 4E 1
MOV D, M 56 1
MOV E, M 5E 1
MOV H, M 66 1
MOV L, M 6E 1

It occupies only 1-Byte in memory. MOV E, M is an example instruction of this type. It is a 1-Byte instruction. Suppose E register content is DBH, H register content is 40H, and L register content is 50H. Let us say location 4050H has the data value AAH. When the 8085 executes this instruction, the contents of E register will change to AAH, as shown below.

Before After

(E)

DBH AAH

(HL)

4050H 4050H

(4050H)

AAH AAH

Address Hex Codes Mnemonic Comment
2008 2A MOV E, M Comment E <- Content of the memory location pointed by HL register pair

The timing diagram for this MOV E, M instruction is as follows −

Mov RM

Summary − So this instruction MOV E, M requires 1-Byte, 2-Machine Cycles (Opcode Fetch, Memory Read) and 7 T-States for execution as shown in the timing diagram.

raja
Published on 30-Nov-2018 07:04:08
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