;
;	utility routine to drive an RC servo 
;	- asumptions - P1.7 ;	  wired to the white wire on the servo, the red wire (power)
;	  is wired to 6V and the black wire is connected to ground.
;
;	calling conventions:
;		always clear carry on return
;		r1:r0	width of pulse in (11/12)uS 
;
;	the servo signal is a 1-2mS (depending on the stick positioon)
;	pulse every 20mS or so - we measure the pulse by waiting for it
;	to start then turning on the timer, and using the signal to gate
;	the result.
;
;	low values return ~0x3c0 high ones ~0x630
;
;	uses timer #0 as a side effect, leaves it idle
;
;	for the record with a 11MHz rock there are 916.66666 timer clocks/mS
;	
put_rcout:	
	clr	p1.7		; make it an input

	clr	tr0		; turn off timer #0
	clr	ie0
	clr	it0

	mov	a, r0
	xrl	a, #0xff
	mov	tl0, a
	mov	a, r1
	xrl	a, #0xff
	mov	th0, a
	mov	a, tmod		; set tmod
	anl	a, #0xf0
	orl	a, #0x01
	mov	tmod, a
	clr	tf0
	setb	p1.7
	setb	tr0
rco1:	jnb	tf0, rco1
	clr	p1.7
	clr	tr0
	clr	c
	ret