.mcall .readw,.writw,.close,.print
	.mcall .csigen,.exit,.sreset

	errbyte = 52
	nwords = 256.

nib:	.word	0
rblk:	.word	0
wblk:	.word	0

start:	.csigen	#dspace,#dext

	mov #wbuff,r3
	mov #nwords,r0
$0:	clr (r3)+
	sob r0,$0

read:
	.readw	#area,#3,#rbuff,#nwords,rblk
	inc	rblk
	bcc	trans
	tstb	@#errbyt
	beq	done
	.print	#rerr
	br	exit

trans:
	mov #rbuff,r1
	mov #nwords*2,r2

loop:	movb (r1)+,r0

	cmp #12,r0
	beq cont
	cmp #15,r0
	beq cont

	sub #'a,r0
	bcs $10
	sub #'a-'A,r0
$10:	add #'a,r0

	sub #'A,r0
	bcc $1
	add #'A-'0,r0
	br $2
$1:	add #10.,r0
$2:

	mov nib,r3
	ash #-1,r3
	bit #1,nib
	bne $4

	ash #4,r0
	bic #017,r0
	movb r0,wbuff(r3)
	inc nib
	br cont

$4:	bic #360,r0
	bisb wbuff(r3),r0
	movb r0,wbuff(r3)

	inc nib
	cmp #nwords*4,nib
	bne cont

	.writw	#area,#0,#wbuff,#nwords,wblk
	inc	wblk
	bcc	$5
	.print	#werr
	br	exit

$5:	mov #wbuff,r3
	mov #nwords,r0
$6:	clr (r3)+
	sob r0,$6

	clr nib

cont:	sub #1,r2
	bne loop
	br read


done:	tst nib
	bne close

	.writw	#area,#0,#wbuff,#nwords,wblk
	bcc	close
	.print	#werr
	br	exit

close:	.close	#0
	.print	#donem

exit:	.sreset
	.exit

dext:	.word	0,0,0,0

area:	.word	0
	.word	0
	.word	0
	.word	0
	.word	0

rbuff:	.blkw	256.
wbuff:	.blkw	256.

rerr:	.asciz	/ read error /
werr:	.asciz	/ write error /
donem:	.asciz	/ complete /

	.even
dspace:

	.end	start