PULSES.ASM

;THIS ROUTINE GENERATES 2 PULSES TO DRIVE THE NINTENDO KEY CHIP FOILER.
;THE PULSES MUST BE ON THE LS377 PIN Q3 WITH PIN Q2 USED AS A BLEED TO
;RAISE THE KEY INPUT BACK TO +5.  THE PAGEING SOFTWARE MUST KEEP THESE
;PINS HIGH WHEN NOT IN USE.

	JSR	XPULSE
	JSR	XPULSE
	LDA	#12
	STA	TWELVE
	JMP	XEXIT

;THIS ROUTINE GENERATES A .005 SECOND HIGH AND THEN LOW PULSE.

XPULSE:	LDA	#8
	STA	EIGHT
	JSR	DELAY005
	LDA	#0
	STA	ZERO
	JSR	DELAY005
	RTS

;THIS ROUTINE DELAYS .0025 SECONDS.

DELAY005:
      	LDY	#4
	LDX	#58		;(MAKES 3*256 + 1*58)
XXX10:	DEX
	BNE	XXX10
	DEY
	BNE	XXX10
	RTS

ZERO:	.byte	0
EIGHT:	.byte	8
TWELVE:	.byte	12

XEXIT: