Datasheet

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Instruction Set Description

4.6.3.33 SUBCX

SUBCX.A Subtract source address-word with carry from destination address-word

SUBCX.[W] Subtract source word with carry from destination word

SUBCX.B Subtract source byte with carry from destination byte

SUBCX.A src,dst

Syntax

SUBCX src,dst or SUBCX.W src,dst

SUBCX.B src,dst

Operation (.not. src) + C + dst → dst or dst – (src – 1) + C → dst

Description The source operand is subtracted from the destination operand. This is made by adding

the 1s complement of the source + carry to the destination. The source operand is not

affected, the result is written to the destination operand. Both operands may be located

in the full address space.

Status Bits N: Set if result is negative (MSB = 1), reset if positive (MSB = 0)

Z: Set if result is zero, reset otherwise

C: Set if there is a carry from the MSB, reset otherwise

V: Set if the subtraction of a negative source operand from a positive destination

operand delivers a negative result, or if the subtraction of a positive source operand

from a negative destination operand delivers a positive result, reset otherwise (no

overflow).

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

Example A 20-bit constant 87654h is subtracted from R5 with the carry from the previous

instruction.

SUBCX.A #87654h,R5 ; Subtract 87654h + C from R5

Example A 48-bit number (3 words) pointed to by R5 (20-bit address) is subtracted from a 48-bit

counter in RAM, pointed to by R7. R5 auto-increments to point to the next 48-bit number.

SUBX.W @R5+,0(R7) ; Subtract LSBs. R5 + 2

SUBCX.W @R5+,2(R7) ; Subtract MIDs with C. R5 + 2

SUBCX.W @R5+,4(R7) ; Subtract MSBs with C. R5 + 2

Example Byte CNT is subtracted from the byte R12 points to. The carry of the previous instruction

is used. 20-bit addresses.

SUBCX.B &CNT,0(R12) ; Subtract byte CNT from @R12

251

SLAU144J–December 2004–Revised July 2013 CPUX

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