16 Bit Subraction

Suraj143 · Nov 3, 2008

I have a 16bit subtract code. Can I tell one of the values greater or less than by looking at the CARRY bit?

I dont need the result I need to know what value is bigger or less.

Code:

Num_L,Num_H	=value to be subtracted

NumF_L,NumF_H	=fix value


[Num_H] [Num_L]= [Num_H] [Num_L] - [NumF_H] [NumF_L]

Sub16	movf	NumF_L,W
	subwf	Num_L,F
	movf	NumF_H,W
	btfss	STATUS,C
	addlw	.1
	subwf	Num_H,F
	btfss	STATUS,C

	;if carry set [Num_H] [Num_L] bigger
	;if carry not set [NumF_H] [NumF_L] bigger

Pommie · Nov 3, 2008

when I don't need to know the result I use,

Code:

		movfw	Num1H		;compare high bytes
		subwf	Num2H,W
		btfss	STATUS,Z	;if same compare low bytes
		goto	GotResult
		movfw	Num1L
		subwf	Num2L,W
GotResult
;carry Set if Num1<=Num2

Mike.

Suraj143 · Nov 3, 2008

Pommie said:
when I don't need to know the result I use,

Code:

movfw Num1H ;compare high bytes subwf Num2H,W btfss STATUS,Z ;if same compare low bytes goto GotResult movfw Num1L subwf Num2L,W GotResult ;carry Set if Num1<=Num2

Mike.

Thats exactly what I need thanks for that.

16 Bit Subraction

Suraj143

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Pommie

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Suraj143

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16 Bit Subraction

Suraj143

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