Datasheet

Instruction set ST7LITE20F2 ST7LITE25F2 ST7LITE29F2
110/170 DocID8349 Rev 7
12 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
Immediat
e
−−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