In SX Microcontrollers, SX/B Compiler and SX-Key Tool, peterverkaik wrote:

The even parity calculation is done by this small routine.
Remember, odd parity is inverted even parity.
For 7databits, bit7 is cleared before entering this code.
(a 0 bit has no effect)

 ; calculate even parity for w
	; result in temp.0
	;---------------------------------------------------------------------------------
even_parity
			mov	temp,w


	;calculation code by John Payson, as found on sxlist.com
	;This routine will leave the parity of temp in temp.0
	;while blenderizing most of the rest of temp


			mov	w,<>temp	; temp = abcdefgh
			xor	temp,w
			mov	w,>>temp
			xor	temp,w


	; at this point, the parity for half the bits
	; (a, b, e, and f) is in bit 2 of temp, and the
	; parity for the other half (bits c, d, g, and h)
	; is in bit 0 of temp.


			snb	temp.2		; if the parity of (a,b,e,f) is 0,
                        			; then the parity of (a,b,c,d,e,f,g,h)
                        			; is equal to the parity of (c,d,g,h)...
                        			; which is already in bit 0, so skip ahead.


			inc	temp		; otherwise, the parity of (a,b,e,f) is 1,
						; so the parity of (a,b,c,d,e,f,g,h) is
						; NOT equal to the parity of (c,d,g,h).
						; invert bit 0.


	; at this point, bit 0 contains the parity of
	; (a,b,c,d,e,f,g,h).


			retp

regards peter

---------- End of Message ----------


You can view the post on-line at:
http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=110792#m111054

Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com

The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)