ST72E121 datasheet(77/92 Pages) STMICROELECTRONICS

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ST72E121 ST72T121

ST7 ADDRESSING MODES (Cont’d)

5.1.6 Indirect Indexed (Short, Long)

This is a combination of indirect and short indexed

addressing modes. The operand is referenced by

its memory address, which is defined by the un-

signed addition of an index register value (X or Y)

with a pointer value located in memory. The point-

er address follows the opcode.

The indirect indexed addressing mode consists of

two sub-modes:

Indirect Indexed (Short)

The pointer address is a byte, the pointer size is a

byte, thus allowing 00 - 1FE addressing space,

and requires 1 byte after the opcode.

Indirect Indexed (Long)

The pointer address is a byte, the pointer size is a

word, thus allowing 64 Kbyte addressing space,

and requires 1 byte after the opcode.

Table

20.

Instructions

Supporting

Direct,

Indexed,

Indirect

and

Indirect

Indexed

Addressing Modes

5.1.7 Relative mode (Direct, Indirect)

This addressing mode is used to modify the PC

it.

The relative addressing mode consists of two sub-

modes:

Relative (Direct)

The offset is following the opcode.

Relative (Indirect)

The offset is defined in memory, which address

follows the opcode.

Lon g and Short

Instructions

Function

Load

Compare

AND, OR, XOR

Logical Operations

ADC, ADD, SUB, SBC

Arithmetic Addition/subtrac-

tion operations

BCP

Bit Compare

Short Instructions Only

Functio n

CLR

Clear

INC, DEC

Increment/Decrement

TNZ

Test Negative or Zero

CPL, NEG

1 or 2 Complement

BSET, BRES

Bit Operations

BTJT, BTJF

Bit Test and Jump Opera-

tions

SLL, SRL, SRA, RLC,

RRC

Shift and Rotate Operations

SWAP

Swap Nibbles

CALL, JP

Call or Jump subroutine

Available Relative Direct/

Indirect Instructions

Function

JRxx

Conditional Jump

CALLR

Call Relative

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