Absolute Value

[beamrider]

Anyone have any example code to calculate the absolute value of a number in 6502 assembly.

e.g. abs(x2 - x1) to derive distance between two 8-bit numbers

[Mike]

For abs(x2-x1), I'm using this code snippet in my Bresenham line plotters:

Code: Select all

 SEC
 LDA x1
 SBC x2
 BCS positive
 EOR #$FF     ; C flag is clear here,
 ADC #$01     ; form two's complement
.positive
 STA dx

... with the absolute value now being stored in dx. x1 and x2 are both unsigned 8-bit values.

[beamrider]

For abs(x2-x1), I'm using this code snippet in my Bresenham line plotters:

Code: Select all

 SEC
 LDA x1
 SBC x2
 BCS positive
 EOR #$FF     ; C flag is clear here,
 ADC #$01     ; form two's complement
.positive
 STA dx

... with the absolute value now being stored in dx. x1 and x2 are both unsigned 8-bit values.

perfect..thanks...