;	TITLE	"SCATH - Syslib 4.0"
	NAME	('CATH')
;=================================================================
;   The Libraries, Version 4, (C) 1989 by Alpha Systems Corp.
;-----------------------------------------------------------------
; Author  : Harold F. Bower
;		Derived from SCATH.Z80 Ver 1.1 by Richard Conn
; Date    : 17 Sep 89
; Version : 1.2
; Module  : SCATH
; Abstract:  This module contains the routine CATH which returns
;	the 4-bit binary (Hexidecimal) value of the character
;	passed to it, or a space if the character is not '0'-'9'
;	or 'A'-'F'.  Note that this routine will NOT accept
;	lower case letters, so CAPS should be passed to enable
;	both cases to work.
; Revision:
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
; Module Entry Points

	PUBLIC		CATH

	.Z80
	CSEG
;===============================================================
; NAME - CATH
; Entry:  A - Contains the character to convert
; Exit :  A = 0000B to 1111B if Valid character entered
;		 A = ' ' (20H) if invalid character
; Uses : AF
; Special Requirements: None
;===============================================================

CATH:	SUB	'0'		; Convert 0-9
	JR	C,ERROR		; Invalid char
	CP	10		; 0-9?
	RET	C
	SUB	7		; Convert A-F
	CP	10
	JR	C,ERROR
	CP	16		; A-F?
	RET	C		; Return if valid
			; ..Fall thru on error
ERROR:	LD	A,' '		; Error char
	RET

	END