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Instruction Set
SUB[.W]
Subtract source from destination
SUB.B
Subtract source from destination
Syntax
SUB
SUB.B
Operation
dst + .NOT.src + 1 −> dst
or
[(dst − src −> dst)]
Description
The source operand is subtracted from the destination operand by adding the
source operand's 1s complement and the constant 1. The source operand is
not affected. The previous contents of the destination are lost.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if result is zero, reset otherwise
C: Set if there is a carry from the MSB of the result, reset otherwise.
V: Set if an arithmetic overflow occurs, otherwise reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
Example
See example at the SBC instruction.
Example
See example at the SBC.B instruction.
Note: Borrow Is Treated as a .NOT.
The borrow is treated as a .NOT. carry :
RISC 16−Bit CPU
3-66
src,dst
or
src,dst
Set to 1 if no borrow, reset if borrow.
SUB.W
src,dst
Borrow
Carry bit
Yes
0
No
1
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