keyboard interrupt demo for FAP Z80 computer

kb.z80

	include 	helper.z80
	
	org	0x0
	jmp	program_start

	org	0x10		; interrupt vector table
	.dw	0x3000		; keyboard interrupt at 0x3000

	org	0x100
program_start:
	ld	a, 0
	ld	i, a		; load interrupt register
	ld	sp, 0x7fff	; set up stack
	im	2		; select interupt mode 2
	call	enable_vram_copy

	ei			; enable interrupt

	ld	d, 0		
	ld	e, 0
	ld	b, 0x39		; set text color to orange

end:	jp	end		; do nothing

kb_isr:				; keyboard ISR at 0x3000
	org	0x3000
	di			; disable interrupt first
	in 	a, (0)		; read keyboard port
	ld	c, a		; print it on screen
	call	print
	ei			; enable interrupt again
	reti