SX Microcontroller Math Method

Two's complemnt of a 32 bit word (4 bytes)

;unknown author, please step forward

	not	var	;Complement all bytes
	not	var+1
	not	var+2
	not	var+3

	inc	var	;Inc. low byte always
	snb	Z	;Skip if no carry to higher bytes
	inc	var+1	;Carry to next byte
	snb	Z
	inc	var+2
	snb	Z
	inc	var+3