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MICROPROCESSOR INSTRUCTION REFERENCE->SUBB

SUBB           Subtract with Borrow A,<source byte>

Subtract source byte and carry flag from accumulator and store result in accumulator.

Formats:
    
DescriptionMnemonicBytesCycles
    
Subtract Immediate Data:SUBB A,#<data>21
Subtract Indirect Address:SUBB A,@Ri11
Subtract Register:SUBB A,Rn11
Subtract Memory:SUBB A,<direct address>21

where Ri is R0 or R1 and Rn is R0 - R7
    
PSW:CACF0RS1RS0OVP
**N/AN/AN/A**
(N/A: Not affected)

Carry (C) (borrow) is set if a borrow is needed for bit 7, else it is cleared.
Auxiliary carry (AC) is set if a borrow is needed for bit 3, else it is cleared.
Overflow (OV) is set if a borrow is needed into bit 6 but not into bit 7 or into bit 7 but not into bit 6.