gistfile1.asm

/////////////////
// CPU Interrupt Service Routine
//

INT2_vect:

    // Save registers
	push	accum
	in		accum,SREG
	push	accum

	in		accum,PORTD
	push	accum
	in		accum,DDRD
	push	accum

	push	XL
	push	XH

	// Enable the CPU's bus access
	cbi		PORTB,cpuBusAllow

	// Read the data from the CPU
	ldi		accum,0x00
	out		DDRD,accum
	ldi		accum,0xff
	out		PORTD,accum
	nop
	in		accum,PIND

	// Enqueue to command buffer
	lds		XL,CMDBUFFER_E
	ldi		XH,CMDBUFFER_H
	st		X,accum

	inc		XL
	sts		CMDBUFFER_E,XL

	// Disable the CPU's bus access
	sbi		PORTB,cpuBusAllow

	// Restore registers
	pop		XH
	pop		XL

	pop		accum
	out		DDRD,accum
	pop		accum
	out		PORTD,accum

	pop		accum				
	out		SREG,accum
	pop		accum

	reti