Page 150 - DCAP210_INTRODUCTION__TO_MICROPROCESSORS

Introduction to Microprocessors

Notes (a) Machine code Opcode Operands

21 LXI H, 8000H
00
80
70 MOV M, B

(b) Machine code Opcode Operands
11 LXI D, 8000H 00
80
78 MOV A, B

12 STAX D

10.3 Additional Arithmetic Operations

Simple arithmetic operations describe the operations between numbers or contents of the
microprocessor register. The advanced arithmetic operations include memory as one of its operand.
The arithmetic instructions referenced to memory perform two tasks:
(a) Copy a byte from a memory location to the microprocessor.
(b) Perform arithmetic operation.

10.3.1 Related to Memory

ADD and SUB instructions implicitly assume that one of the operand is register A i.e., Accumulator.
After an operation, the previous contents of the Accumulator are replaced by the result. All the
flags are modified according to the result.

Table 10.4: List of Memory Related Arithmetic Operations.

Opcode Operands Description

ADD M Add memory contents
(a) It is a 1-byte instruction.
(b) Adds (M) to (A) and stores result in A.
(c) Contents of HL register specifies the memory
location.
SUB Subtract memory
(a) It is a 1-byte instruction.
(b) Subtract (M) from (A) and stores the result in
A
(c) Contents of HL register specifies the memory
location.
INR M Increments memory contents
(a) It is a 1-byte instruction
(b) Increments the contents of memory by 1, not
the memory address
(c) (HL) register specifies the memory location.
Contd. ...

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