 8051 Instruction Set Manual |
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| DECThe DEC instruction decrements the specified operand by 1. An original value of 00h underflows to 0FFh. No flags are affected by this instruction. Note When this instruction is used to modify an output port, the value used as the port data is read from the output data latch, not the pins of the port. See Also: INC | Bytes | 1 | | Cycles | 1 | | Encoding | | | Operation |
DEC
(Ri) = (Ri) - 1
| | Example |
DEC @R1
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| Bytes | 1 | | Cycles | 1 | | Encoding | | | Operation |
DEC
A = A - 1
| | Example |
DEC A
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| Bytes | 2 | | Cycles | 1 | | Encoding | | | Operation |
DEC
(direct) = (direct) - 1
| | Example |
DEC 35h
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| Bytes | 1 | | Cycles | 1 | | Encoding | | | Operation |
DEC
Rn = Rn - 1
| | Example |
DEC R7
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