6502 Pen plotter - Initialisation by Lee Davison
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Initialisation is simple. All that needs to be done is to disable interrupts, disable the motors and lift the pen, clear the timers and set the LED port.

Initdraw
	SEI			; disable interrupts

	LDA	#$10		; set byte
	STA	Mport		; turn off motors, lift pen

	LDA	#$01		; turn on power LED, turn off alarm LED
	STA	Pport		; out to LED port
	STA	Timer2r		; set access to timer1 control register
	STA	Timer13r	; software reset timers

	LDA	#$00		; clear byte
	STA	Timer13r	; allow timers to run
	STA	Lastp		; set last pen setting
	STA	Drawf		; clear draw flag
	STA	BRindx		; clear read index
	STA	BWindx		; clear write index

	RTS

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