Page 132 - DCAP210_INTRODUCTION__TO_MICROPROCESSORS

Introduction to Microprocessors

Notes impression that the contents of the source are destroyed when, in fact, the contents are retained
without any modification. The various types of data transfer (copy) are listed below together
with examples of each type:

Types Examples
1. Between Registers. 1. Copy the contents of the register B
into register D.

2. Specific data byte to a register or a 2. Load register B with the data byte 32H.
memory location.

3. Between a memory location 3. From a memory location 2000H
and a register. to register B.
4. Between an I/O device and the 4. From an input keyboard to the
accumulator. accumulator.

The data transfer instructions move data between registers or between memory and registers.
MOV: Move

MVI: Move Immediate
LDA: Load Accumulator Directly from Memory
STA: Store Accumulator Directly in Memory
LHLD: Load H & L Registers Directly from Memory

SHLD: Store H & L Registers Directly in Memory
An ‘X’ in the name of a data transfer instruction implies that it deals with a register pair (16-bits);

LXI: Load Register Pair with Immediate data
LDAX: Load Accumulator from Address in Register Pair
STAX: Store Accumulator in Address in Register Pair
XCHG: Exchange H & L with D & E

XTHL: Exchange Top of Stack with H & L

The microprocessor, also known as a CPU (central processing unit).

9.2 Arithmetic Operations

These instructions perform arithmetic operations such as addition, subtraction, increment, and
decrement.

Addition: Any 8-bit number, or the contents of a register or the contents of a memory location
can be added to the contents of the accumulator and the sum is stored in the accumulator. No two
other 8-bit registers can be added directly (e.g., the contents of register B cannot be added directly
to the contents of the register C). The instruction DAD is an exception; it adds 16-bit data directly
in register pairs.
Subtraction: Any 8-bit number, or the contents of a register, or the contents of a memory location
can be subtracted from the contents of the accumulator and the results stored in the accumulator.
The subtraction is performed in 2’s compliment, and the results if negative, are expressed in 2’s
complement. No two other registers can be subtracted directly.

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