gistfile1.asm

mainloop:

    // Wait for VBL to process commands
	sbrs	VBL,0
	rjmp	mainloop

	// See if there's a command pending
	lds		regS,CMDBUFFER_S
	lds		regT,CMDBUFFER_E

	cp		regS,regT
	breq	mainloop		// No command at all
	inc		regS
	cp		regS,regT
	breq	mainloop		// Half a command- keep waiting

	// Dequeue the command from the buffer
	dec		regS
	mov		XL,regS
	ldi		XH,CMDBUFFER_H
	ld		cmdBufferL,X
	inc		XL				// Not using X+ because we want to wrap the low byte
	ld		cmdBufferH,X

	inc		XL
	sts		CMDBUFFER_S,XL

	// Switch on command buffer value
	cpi		cmdBufferL,0x01
	breq	redirectTR1
	cpi		cmdBufferL,0x02
	breq	redirectTR2
	cpi		cmdBufferL,0x03
	breq	redirectTR3
	cpi		cmdBufferL,0x04
	breq	redirectTR4