ST72325_07 Datasheet, PDF (139/196 Pages) STMicroelectronics – 8-bit MCU with 16 to 60K Flash/ROM, ADC, CSS, 5 timers, SPI, SCI, I2C interface

INSTRUCTION SET OVERVIEW (Cont’d)
11.2 INSTRUCTION GROUPS
The ST7 family devices use an Instruction Set
consisting of 63 instructions. The instructions may
be subdivided into 13 main groups as illustrated in
the following table:
Load and Transfer
Stack operation
Increment/Decrement
Compare and Tests
Logical operations
Bit Operation
Conditional Bit Test and Branch
Arithmetic operations
Shift and Rotates
Unconditional Jump or Call
Conditional Branch
Interruption management
Condition Code Flag modification
LD
PUSH
INC
CP
AND
BSET
BTJT
ADC
SLL
JRA
JRxx
TRAP
SIM
CLR
POP
DEC
TNZ
OR
BRES
BTJF
ADD
SRL
JRT
WFI
RIM
RSP
BCP
XOR
SUB
SRA
JRF
HALT
SCF
CPL NEG
SBC
RLC
JP
MUL
RRC
CALL
SWAP
CALLR
IRET
RCF
SLA
NOP RET
Using a prebyte
The instructions are described with one to four op-
codes.
In order to extend the number of available op-
codes for an 8-bit CPU (256 opcodes), three differ-
ent prebyte opcodes are defined. These prebytes
modify the meaning of the instruction they pre-
cede.
The whole instruction becomes:
PC-2
End of previous instruction
PC-1
Prebyte
PC
Opcode
PC+1
Additional word (0 to 2) according
to the number of bytes required to compute the ef-
fective address
These prebytes enable instruction in Y as well as
indirect addressing modes to be implemented.
They precede the opcode of the instruction in X or
the instruction using direct addressing mode. The
prebytes are:
PDY 90
Replace an X based instruction
using immediate, direct, indexed, or inherent ad-
dressing mode by a Y one.
PIX 92
Replace an instruction using di-
rect, direct bit, or direct relative addressing mode
to an instruction using the corresponding indirect
addressing mode.
It also changes an instruction using X indexed ad-
dressing mode to an instruction using indirect X in-
dexed addressing mode.
PIY 91
Replace an instruction using X in-
direct indexed addressing mode by a Y one.
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