ST72104G, ST72215G, ST72216G, ST72254G
13 INSTRUCTION SET
13.1 ST7 ADDRESSING MODES
so, most of the addressing modes may be subdi-
vided in two sub-modes called long and short:
The ST7 Core features 17 different addressing
modes which can be classified in 7 main groups:
– 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.
Addressing Mode
Inherent
Example
nop
– 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)
Immediate
Direct
ld A,#$55
ld A,$55
Indexed
ld A,($55,X)
ld A,([$55],X)
jrne loop
Indirect
Relative
Bit operation
bset byte,#5
The ST7 Assembler optimizes the use of long and
short addressing modes.
The ST7 Instruction set is designed to minimize
the number of bytes required per instruction: To do
Table 19. ST7 Addressing Mode Overview
Pointer
Address
(Hex.)
Pointer
Size
(Hex.)
Destination/
Source
Length
(Bytes)
Mode
Syntax
Inherent
Immediate
Short
nop
+ 0
+ 1
+ 1
+ 2
ld A,#$55
ld A,$10
Direct
Direct
00..FF
Long
ld A,$1000
0000..FFFF
+ 0 (with X register)
+ 1 (with Y register)
No Offset
Direct
Indexed
ld A,(X)
00..FF
Short
Long
Short
Long
Short
Long
Relative
Relative
Bit
Direct
Indexed
Indexed
ld A,($10,X)
ld A,($1000,X)
ld A,[$10]
00..1FE
+ 1
+ 2
+ 2
+ 2
+ 2
+ 2
+ 1
+ 2
+ 1
+ 2
+ 2
+ 3
Direct
0000..FFFF
00..FF
Indirect
Indirect
Indirect
Indirect
Direct
00..FF
00..FF
00..FF
00..FF
byte
word
byte
word
ld A,[$10.w]
ld A,([$10],X)
0000..FFFF
00..1FE
Indexed
Indexed
ld A,([$10.w],X) 0000..FFFF
1)
1)
jrne loop
PC-128/PC+127
Indirect
Direct
jrne [$10]
PC-128/PC+127
00..FF
00..FF
00..FF
00..FF
byte
byte
byte
bset $10,#7
bset [$10],#7
Bit
Indirect
Direct
00..FF
Bit
Relative btjt $10,#7,skip 00..FF
Relative btjt [$10],#7,skip 00..FF
Bit
Indirect
Note 1. At the time the instruction is executed, the Program Counter (PC) points to the instruction follow-
ing JRxx.
90/140
ETC [ ETC ]
