Page 147 - DCAP210_INTRODUCTION__TO_MICROPROCESSORS

Unit 10: Programming Techniques with Additional Instructions

5A ; destination, Starting Notes
40 ; at last location
06 MVI B, 06H ; Byte counter
06
7E NEXT: MOV A, M ; Get data byte
12 STAX D ; Store data byte
23 INX H ; Next location

1B DCX D
05 DCR B ; Next count
C2 JNZ NEXT ; If counter is not 0, go
X ; back to transfer next byte
X
76. HLT ; End of program.

10.2 Additional Data Transfer Instructions

Additional data transfer instructions are between the microprocessor and memory.

10.2.1 16-bit Data Transfer to Registers Pairs
This is done with LXI mnemonic of assembly language. LXI is similar to MVI instruction except
LXI loads 16-bit data in register pairs and the stack pointer register. No flags are affected by these
instructions. LXI is a 3-byte instruction where as MVI is a 2-byte instruction.
Table 10.1 List of Instructions of 16-bit Data Transfer to Register Pairs (LXI).

Opcode Operand Description

LXI R, 16-bit Load Register Pair Immediate
LXI B, 16-bit (a) It is a 3-byte instruction
LXI D, 16-bit (b) Second byte is loaded in the low-order register
of the register pair
LXI H, 16-bit (c) Third byte is loaded in the high-order register
of the register pair.

LXI SP, 16-bit (d) The operands B, D, H, represents BC, DE, HL
registers and SP represents the stack pointer
register.

The basic difference between MVI and LXI are:
1. LXI can load 16-bit data in register pairs and stack pointer register where as MOV can copy
data from source register to destination register and MVI can load 8-bit data into the specified
register.
2. LXI is a 3-byte instruction whereas MVI and MOV are 2-byte and 1-byte instructions.

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