ST7MC1 Datasheet, PDF (243/308 Pages) STMicroelectronics – 8-BIT MCU WITH NESTED INTERRUPTS, FLASH, 10-BIT ADC, BRUSHLESS MOTOR CONTROL, FIVE TIMERS, SPI, LINSCI

ST7MC1/ST7MC2
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
SBC
RLC
JP
IRET
RCF
NEG
MUL
RRC
CALL
SWAP
CALLR
SLA
NOP RET
Using a pre-byte
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.
11.2.1 Illegal Opcode Reset
In order to provide enhanced robustness to the de-
vice against unexpected behaviour, a system of il-
legal opcode detection is implemented. If a code to
be executed does not correspond to any opcode
or prebyte value, a reset is generated. This, com-
bined with the Watchdog, allows the detection and
recovery from an unexpected fault or interference.
Note: A valid prebyte associated with a valid op-
code forming an unauthorized combination does
not generate a reset.
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