ST7FLITE25F1B6 datasheet(110/166 Pages) STMICROELECTRONICS

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Instruction set

ST7LITE20F2 ST7LITE25F2 ST7LITE29F2

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Doc ID 8349 Rev 5

Instruction set

12.1

ST7 addressing modes

The ST7 Core features 17 different addressing modes which can be classified in seven main

groups:

The ST7 Instruction set is designed to minimize the number of bytes required per

instruction: To do so, most of the addressing modes may be subdivided in two submodes

called long and short:

●

Long addressing mode is more powerful because it can use the full 64 Kbyte address

space, however it uses more bytes and more CPU cycles.

●

Short addressing mode is less powerful because it can generally only access page

zero (0000h00FFh range), but the instruction size is more compact, and faster. All

memory to memory instructions 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 48.

Addressing mode groups

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

Table 49.

ST7 addressing mode overview

Mode

Syntax

Destination/

source

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 (with x register)

+ 1 (with Y register)

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

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