Regulus Berdin [rberdin at BIGFOOT.COM]

this is 2x faster (500kbps @ 4MHz) :

; serial tx
; assumes PORTB1 initially on high state

	mov	W, >>data
	xor	data, W

	mov	W, #1
	xor	RB, W	;start bit

	snb	C
	xor	RB, W	;b0

	snb	data.0
	xor	RB, W	;b1

	snb	data.1
	xor	RB, W	;b2

	snb	data.2
	xor	RB, W	;b3

        .
        .
        .

	nop
	setb	RB.0	;