KS57C2308/P2308/C2316/P2316 SAM47 INSTRUCTION SET
5-81
SBC — Subtract With Carry
SBC (Continued)
Examples: 3. If SBC A,@HL is followed by an ADS A,#im, the SBC skips on “no borrow” to the instruction
immediately after the ADS. An “ADS A,#im” instruction immediately after the “SBC A,@HL”
instruction does not skip even if an overflow occurs. This function is useful for decimal
adjustment operations.
a. 8 – 6 decimal addition (the contents of the address specified by the HL register is 6H):
RCF ;C ← "0"
LD A,#8H ;A ← 8H
SBC A,@HL ;A ← 8H – 6H – C(0) = 2H, C ← "0"
ADS A,#0AH ;Skip this instruction because no borrow after SBC result
JPS XXX
b. 3 – 4 decimal addition (the contents of the address specified by the HL register is 4H):
RCF ;C ← "0"
LD A,#3H ;A ← 3H
SBC A,@HL ;A ← 3H – 4H – C(0) = 0FH, C ← "1"
ADS A,#0AH ;No skip. A ← 0FH + 0AH = 9H
;(The skip function of “ADS A,#im” is inhibited after a
;“SBC A,@HL” instruction even if an overflow occurs.)
JPS XXX