ST72T331 STMICROELECTRONICS [STMicroelectronics], ST72T331 Datasheet - Page 89

• Manufacturer Part Number: ST72T331
• Description: 8-BIT MCU WITH 8 TO 16K OTP/EPROM, 256 EEPROM, 384 TO 512 BYTES RAM, ADC, WDG, SCI, SPI AND 2 TIMERS
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

6.2 INSTRUCTION GROUPS
The ST7 family devices use an Instruction Set
consisting of 63 instructions. The instructions may
Using a pre-byte
The instructions are described with one to four
bytes.
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:
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
Code Condition Flag modification
PC-2 End of previous instruction
PC-1 Prebyte
PC
PC+1 Additional word (0 to 2) according to the
Opcode
number of bytes required to compute the
effective address
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
be subdivided into 13 main groups as illustrated in
the following table:
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:
RSP
BCP
XOR
SUB
SRA
JRF
HALT
SCF
PDY 90 Replace an X based instruction using
PIX 92 Replace an instruction using direct, di-
PIY 91 Replace an instruction using X indirect
CPL
SBC
RLC
JP
IRET
RCF
immediate, direct, indexed, or inherent
addressing mode by a Y one.
rect bit, or direct relative addressing
mode to an instruction using the corre-
sponding indirect addressing mode.
It also changes an instruction using X
indexed addressing mode to an instruc-
tion using indirect X indexed addressing
mode.
indexed addressing mode by a Y one.
CALL
NEG
MUL
RRC
ST72E331 ST72T331
SWAP
CALLR
SLA
NOP
RET
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