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STM8 addressing modes

PM0044

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Doc ID 13590 Rev 3

STM8 addressing modes

The STM8 core features 18 different addressing modes which can be classified in 8 main

groups:

The STM8 Instruction set is designed to minimize the number of required bytes per

instruction. To do so, most of the addressing modes can be split in three sub-modes called

extended, long and short:

●

The extended addressing mode ("e") can reach any byte in the 16-Mbyte addressing

space, but the instruction size is bigger than the short and long addressing mode.

Moreover, the number of instructions with this addressing mode (far) is limited (CALLF,

RETF, JPF and LDF)

●

The long addressing mode ("w") is the most powerful for program management, when

the program is executed in the same section (same PCE value). The long addressing

mode is optimized for data management in the first 64-Kbyte addressing space (from

0x000000 to 0x00FFFF) with a complete set of instructions, but the instruction size is

bigger than the short addressing mode.

●

The short addressing mode ("b") is less powerful because it can only access the page

zero (from 0x000000 to 0x0000FF), but the instruction size is more compact.

Table 16.

STM8 core addressing modes

Addressing mode groups

Example

Inherent

NOP

Immediate

LD A,#$55

Direct

LD A,$55

Indexed

LD A,($55,X)

SP Indexed

LD A,($55,SP)

Indirect

LD A,([$55],X)

Relative

JRNE loop

Bit operation

BSET byte,#5

Table 17.

STM8 addressing mode overview

Mode

Syntax

Destination

address

Pointer

address

Inherent

NOP

Immediate

LD A,#$55

Short

Direct

LD A,$10

000000..0000FF

Long

Direct

LD A,$1000

000000..00FFFF

Extended

Direct

LDF A,$100000

000000..FFFFFF

No Offset

Direct

Indexed

LD A,(X)

000000..00FFFF

Short

Direct

Indexed

LD A,($10,X)

000000..0100FE

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