nor
NOR - 7C 00 00 F8
nor
Instruction Syntax
| Mnemonic | Format | Flags |
| nor | rA,rS,rB | Rc = 0 |
| nor. | rA,rS,rB | Rc = 1 |
Instruction Encoding
0
1
1
1
1
1
S
S
S
S
S
A
A
A
A
A
B
B
B
B
B
0
0
0
0
0
0
0
0
0
Rc
| Field | Bits | Description |
| Primary Opcode | 0-5 | 011111 (0x1F) |
| rS | 6-10 | Source register |
| rA | 11-15 | Destination register |
| rB | 16-20 | Source register |
| Reserved | 21-29 | 000000000 |
| Rc | 30-31 | Record Condition Register |
Operation
rA ← ¬((rS) | (rB))
The logical NOR of (rS) and (rB) is placed into rA.
Note: The nor instruction performs a logical NOR operation, which is equivalent to NOT(OR(rS, rB)).
Affected Registers
Condition Register (CR0 field)
(if Rc = 1)
- LT (Less Than)
- GT (Greater Than)
- EQ (Equal)
- SO (Summary Overflow)
Note: CR0 field reflects the result of the logical operation.
Examples
Basic NOR Operation
nor r3, r1, r2 # r3 = NOT(r1 OR r2) nor. r3, r1, r2 # Same as above, but also sets condition register
Bit Clearing
# Clear specific bits in r1 using a mask in r2 nor r3, r1, r2 # r3 = NOT(r1 OR r2) # This can be used to clear bits that are set in r2
Logical Operations
# NOR can be used to implement other logical operations # NOT r1: nor r2, r1, r1 # r2 = NOT(r1) # NAND r1, r2: nor r3, r1, r2 # r3 = NOT(r1 AND r2)