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Instruction Set Description
4.6.3.31 SBCX
* SBCX.A
Subtract borrow (.NOT. carry) from destination address-word
* SBCX.[W]
Subtract borrow (.NOT. carry) from destination word
* SBCX.B
Subtract borrow (.NOT. carry) from destination byte
SBCX.A dst
Syntax
SBCX dst
or
SBCX.W dst
SBCX.B dst
Operation
dst + 0 C
→
dst
dst + C
→
dst
dst + 0FFh + C
→
dst
SBCX.A #0,dst
Emulation
SBCX #0,dst
SBCX.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 8-bit counter pointed to by R13 is subtracted from a 16-bit counter pointed to by
R12.
SUBX.B
@R13,0(R12)
; Subtract LSDs
SBCX.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
220
CPUX
SLAU272C – May 2011 – Revised November 2013
Copyright © 2011–2013, Texas Instruments Incorporated