or
OR - 7C 00 00 78
or
Instruction Syntax
| Mnemonic | Format | Flags |
| or | rA,rS,rB | Rc = 0 |
| or. | 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 OR of (rS) and (rB) is placed into rA.
Note: The or instruction performs a logical OR operation on the source operands.
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 OR Operation
or r3, r1, r2 # r3 = r1 OR r2 or. r3, r1, r2 # Same as above, but also sets condition register
Bit Setting
# Set specific bits in r1 using a mask in r2 or r1, r1, r2 # r1 = r1 OR r2 (set bits that are 1 in r2)
Register Copy
# Copy r1 to r2 using OR with zero li r3, 0 # Load immediate 0 or r2, r1, r3 # r2 = r1 OR 0 = r1