Datasheet

Instruction Set

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3.4.6.47 SUBC, SBB

SUBC[.W], SBB[.W] Subtract source and borrow/.NOT. carry from destination

SUBC.B, SBB.B Subtract source and borrow/.NOT. carry from destination

Syntax SUBC src,dst or SUBC.W src,dst or

SBB src,dst or SBB.W src,dst

SUBC.B src,dst or SBB.B src,dst

Operation dst + .NOT.src + C → dst

(dst - src - 1 + C → dst)

Description The source operand is subtracted from the destination operand by adding the source

operand's 1s complement and the carry bit (C). 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.

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 Two floating point mantissas (24 bits) are subtracted.

LSBs are in R13 and R10, MSBs are in R12 and R9.

SUB.W R13,R10 ; 16-bit part, LSBs

SUBC.B R12,R9 ; 8-bit part, MSBs

Example The 16-bit counter pointed to by R13 is subtracted from a 16-bit counter in R10 and

R11(MSD).

SUB.B @R13+,R10 ; Subtract LSDs without carry

SUBC.B @R13,R11 ; Subtract MSDs with carry

... ; resulting from the LSDs

NOTE: Borrow Implementation

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

Yes 0

No 1

110

CPU SLAU144J–December 2004–Revised July 2013

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