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Instruction Set

3.4.6.42 SBC

*SBC[.W] Subtract source and borrow/.NOT. carry from destination

*SBC.B Subtract source and borrow/.NOT. carry from destination

Syntax SBC dst or SBC.W dst

SBC.B dst

Operation dst + 0FFFFh + C → dst

dst + 0FFh + C → dst

Emulation SUBC #0,dst

SUBC.B #0,dst

Description The carry bit (C) is added to the destination operand minus one. 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.

Set to 1 if no borrow, reset if borrow.

V: Set if an arithmetic overflow occurs, reset otherwise.

Mode Bits OSCOFF, CPUOFF,and GIE are not affected.

Example The 16-bit counter pointed to by R13 is subtracted from a 32-bit counter pointed to by

R12.

SUB @R13,0(R12) ; Subtract LSDs

SBC 2(R12) ; Subtract carry from MSD

Example The 8-bit counter pointed to by R13 is subtracted from a 16-bit counter pointed to by

R12.

SUB.B @R13,0(R12) ; Subtract LSDs

SBC.B 1(R12) ; Subtract carry from MSD

NOTE: Borrow Implementation

The borrow is treated as a .NOT. carry: Borrow Carry bit

Yes 0

No 1

105

SLAU144J–December 2004–Revised July 2013 CPU

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