2.Instruction Set List
Instruction Code
Meaning
ADC
Add with carry
AND
Logical AND
ASL
Shift left one bit
BCC
Branch if carry clear
BCS
Branch if carry set
BEQ
Branch if equal to zero
BIT
Bit test
BMI
Branch if minus
BNE
Branch if not equal to zero
BPL
Branch if plus
BRK
Break
BVC
Branch if overflow clear
BVS
Branch if overflow set
CLC
Clear carry
CLD
Clear decimal mode
CLI
Clear interrupt disable bit
CLV
Clear overflow
CMP
Compare accumulator to memory
CPX
Compare with index register X
CPY
Compare with index register Y
DEC
Decrement memory by one
DEX
Decrement index X by one
DEY
Decrement index Y by one
EOR
Logical exclusive-OR
INC
Increment memory by one
INX
Increment index X by one
INY
Increment index Y by one
JMP
Jump to new location
JSR
Jump to subroutine
NT68P81
Operation
A + M + C → A,C
A•M → A
C ← M7•••M0 ← 0
Branch on C=0
Branch on C=1
Branch on Z=1
A•M,M7 → N,M6 → V
Branch on N=1
Branch on Z=0
Branch on N=0
Forced interrupt PC + 2↓ PC↓
Branch on V=0
Branch on V=1
0→ C
0→ D
0→ I
0→ V
A-M
X- M
Y-M
M-1→M
X- 1 → X
Y-1→Y
A ⊕ M→A
M+1 → M
X+1→ X
Y+1 → Y
(PC + 1) → PCL,(PC + 2) → PCH
PC + 2↓,(PC + 1) → PCL,(PC + 2) → PCH
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