ST7232A datasheet(107/157 Pages) STMICROELECTRONICS

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ST7232A

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11 INSTRUCTION SET

11.1 CPU ADDRESSING MODES

The CPU features 17 different addressing modes

which can be classified in 7 main groups:

The CPU Instruction set is designed to minimize

the number of bytes required per instruction: To do

so, most of the addressing modes may be subdi-

vided in two sub-modes called long and short:

– Long addressing mode is more powerful be-

cause it can use the full 64 Kbyte address space,

however it uses more bytes and more CPU cy-

cles.

– Short addressing mode is less powerful because

it can generally only access page zero (0000h -

00FFh range), but the instruction size is more

compact, and faster. All memory to memory in-

structions use short addressing modes only

(CLR, CPL, NEG, BSET, BRES, BTJT, BTJF,

INC, DEC, RLC, RRC, SLL, SRL, SRA, SWAP)

The ST7 Assembler optimizes the use of long and

short addressing modes.

Table 24. CPU Addressing Mode Overview

Addressing Mode

Example

Inherent

nop

Immediate

ld A,#$55

Direct

ld A,$55

Indexed

ld A,($55,X)

Indirect

ld A,([$55],X)

Relative

jrne loop

Bit operation

bset

byte,#5

Mode

Syntax

Destination

Pointer

Address

(Hex.)

Pointer Size

(Hex.)

Length

(Bytes)

Inherent

nop

+ 0

Immediate

ld A,#$55

+ 1

Short

Direct

ld A,$10

00..FF

+ 1

Long

Direct

ld A,$1000

0000..FFFF

+ 2

No Offset

Direct

Indexed

ld A,(X)

00..FF

+ 0

Short

Direct

Indexed

ld A,($10,X)

00..1FE

+ 1

Long

Direct

Indexed

ld A,($1000,X)

0000..FFFF

+ 2

Short

Indirect

ld A,[$10]

00..FF

byte

+ 2

Long

Indirect

ld A,[$10.w]

0000..FFFF

00..FF

word

+ 2

Short

Indirect

Indexed

ld A,([$10],X)

00..1FE

00..FF

byte

+ 2

Long

Indirect

Indexed

ld A,([$10.w],X)

0000..FFFF

00..FF

word

+ 2

Relative

Direct

jrne loop

PC+/-127

+ 1

Relative

Indirect

jrne [$10]

PC+/-127

00..FF

byte

+ 2

Bit

Direct

bset $10,#7

00..FF

+ 1

Bit

Indirect

bset [$10],#7

00..FF

byte

+ 2

Bit

Direct

Relative

btjt $10,#7,skip

00..FF

+ 2

Bit

Indirect

Relative

btjt [$10],#7,skip

00..FF

byte

+ 3

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