UM0144 datasheet(9/92 Pages) STMICROELECTRONICS

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ST7 Assembler Linker

2 ST7 Addressing Modes

UM0144

9/92

Two-operand instructions are coded with destination operand appearing at first position. For

example:

2.3

Short and long addressing modes

For ST7 there are two addressing modes that differ in memory address size (i.e. one byte for

short mode and two bytes for long mode).

Because of these different addressing modes, the target address range of the operands will

depend upon the addressing mode chosen:

Some instructions accept both long and short addressing modes, while others only accept one

or the other.

For example:

For ST7 instructions supporting both short and long formats, when external symbols are

referenced, long mode is chosen by the Assembler. For example:

2.4

Inherent addressing mode

This concept is hardware-oriented, meaning that instruction operands are coded inside the

operation code. At the source coding level, operands are written explicitly.

Examples:

lab01

ld A,memory

; load accumulator A with memory contents

lab02

ld memory,A

; load memory location with A contents

ld X,A

; load X with accumulator contents

0-$FF

for short addressing mode

$100-$FFFF

for long addressing mode

lab10

add

A,memory

; accepts both types of addressing modes

lab11

inc

memory

;

accepts only short addressing mode

EXTERN symb3

;

symb1

equ

$10

;

...

A,symb1

; short mode

A,symb3

; long mode chosen

lab06

push

; put accumulator A onto the stack

lab07

mul

X,A

; multiply X by A

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