UM0144 datasheet(10/92 Pages) STMICROELECTRONICS

10 / 92 page

2 ST7 Addressing Modes

ST7 Assembler Linker

10/92

UM0144

2.5

Immediate operands

Immediate operands permit you to input a specific value for use with an instruction. They are

signaled by the use of a sharp sign (#) before the value.

Examples:

The range for an 8-bit immediate operand is from 0 to 255.

2.6

Direct and indirect modes

A direct addressing mode means that the data byte required to do the operation is found by

its memory address, which follows the op-code.

An indirect addressing mode means that the data byte required to do the operation is found

by its memory address which is located in memory (pointer). The pointer address follows the

op-code.

This last group consists of memory indirect variants:

●

short indirect (short pointed data),

●

long indirect (long pointed data),

●

short indirect indexed (short pointed data),

●

long indirect indexed (long pointed data),

For ST7 devices, the address specified must always be in page 0 (i.e. its address must be less

than $100). Examples:

To make the distinction between short and long indirect addressing mode, the suffix.w is

specified to indicate that you want to work in long indirect mode (this is also true for indexed

addressing mode). Implicitly, if nothing is specified, the short indirect addressing mode is

assumed.

For ST7 devices, you can also use.b to specify short indirect addressing mode (as with the

indexed addressing mode).

lab08

A,#1

; load A with immediate value 1

lab09

bset

memory,#3

; set bit #3 in memory location

btjt

memory,#3,label

;

test bit #3 of memory and

jump if true (set)

A,[80]

; short indirect

A,[80.b]

; short indirect

A,[80.w]

; long

indirect

lab12

equ

A,([lab12],X)

; short indirect X-indexed

A,([lab12.b],X)

; short indirect X-indexed

A,([lab12.w],Y)

; long indirect Y-indexed

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