Datasheet

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Instruction Set Description

4.6.2.46 SUB

SUB[.W] Subtract source word from destination word

SUB.B Subtract source byte from destination byte

Syntax

SUB src,dst or SUB.W src,dst

SUB.B src,dst

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

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

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

affected, the result is written to the destination operand.

Status Bits N: Set if result is negative (src > dst), reset if positive (src ≤ dst)

Z: Set if result is zero (src = dst), reset otherwise (src ≠ dst)

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 16-bit constant 7654h is subtracted from RAM word EDE.

SUB #7654h,&EDE ; Subtract 7654h from EDE

Example A table word pointed to by R5 (20-bit address) is subtracted from R7. Afterwards, if R7

contains zero, jump to label TONI. R5 is then auto-incremented by 2. R7.19:16 = 0.

SUB @R5+,R7 ; Subtract table number from R7. R5 + 2

JZ TONI ; R7 = @R5 (before subtraction)

... ; R7 <> @R5 (before subtraction)

Example Byte CNT is subtracted from byte R12 points to. The address of CNT is within PC ± 32K.

The address R12 points to is in full memory range.

SUB.B CNT,0(R12) ; Subtract CNT from @R12

209

SLAU144J–December 2004–Revised July 2013 CPUX

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