;
; This crc routine updates the checkword in (bc) using the byte
; passed in (a). The checkwords computed are suitable for
; communication with IBM format floppy disks. The two byte checkword
; is produced by the generating polynomial x**16+x**12+x**5+1.  The
; checksum should be initialized to 0ffffh (i.e. 0ffffh is passed in
; bc when the checksum sequence is started). The new checksum is
; returned in (bc).
; a,f,b,c
.crc::	push	d
	xra c	! mov d,a
	rrc 	! rrc ! rrc ! rrc
	ani	0fh;			mask
	xra d	! mov e,a
	rrc	! rrc ! rrc ! mov d,a
	ani 1fh	! xra b ! mov c,a
	mov a,d	! ani 0e0h
	xra e	! mov b,a
	mov a,d	! rrc ! ani 0f0h
	xra c	! mov c,a
	pop	d
	ret