fills up VRAM of FAP's video card

vram_fill_test.z80

	org	0x0		
start:	xor	d
	xor	e
	xor	b		; clear d, e, b
	ld	hl, 0x92c0	; load hl with address of back of the VRAM
	ld	de, 2400	; 2400 bytes of attributes
	ld	b, 0x1b		; color, 0x1b is 011011, should be purple
attri:	ld	(hl), b		; store the color into VRAM address at hl
	dec	hl		; decrease hl to move on to next VRAM address
	dec	de		; decrease the counter
	ld	a,d
	or 	e		; check if counter is 0
	jp	nz,attri	; continue looping if it's not

	ld	de, 2400	; now attributes have been filled, reload the counter
	ld	b, 65		; ASCII code for letter A
char:	ld	(hl), b		; similarly loop as above, fill the chatacter VRAM
	dec	hl
	dec	de
	ld	a,d
	or 	e
	jp	nz,char

end:	jp	end		; all done