;
; Module Name:  MEVALB24
; Author:  Steven Cohen
; Based on Richard Conn's EVAL2
; March 10, 1987
;
	public	EVALB24
	EXT	DOUBLE24,ZEROBUF
;
;  EVALB24
;	Convert a string of ASCII binary digits 
; into a binary value; string is converted until invalid digit is
; encountered.  
;
;       INPUT:  DE POINTS TO a 3-byte buffer in which the converted
; 		value is to be stored.
;		HL POINTS TO the first byte of the string to be converted
;       OUTPUT: HL points to error character if any
;		A contains the lowest order 8 bits of the value
;		carry flag set indicates error
;
EVALB24:
	PUSH	BC	; SAVE BC
	CALL	ZEROBUF
;  Get next digit and check for '0' - '1'
E2L:
	LD	A,(HL)	; GET BYTE
	SUB	'0'
	CP	0		; CHECK FOR RANGE
	JR	C,DONE
	CP	2	; CHECK FOR RANGE
	JR	NC,DONE

;  Multiply buffer by 2
MUL2:
	PUSH	DE
	PUSH	HL
	PUSH	AF	; SAVE VALUE
	EX	DE,HL
	CALL	DOUBLE24
;
;  Add in A
;
	LD	A,(HL)	; get low-order digit
	LD	B,A	; preserve in B
	POP	AF	; GET LATEST DIGIT
	OR	B	; or in latest digit
	LD	(HL),A	; put it in buffer
	POP	HL
	POP	DE
;
;  Continue
;
	INC	HL	; PT TO NEXT CHARACTER
	JP	E2L
;
;  Done -- Result already in buffer pted to by DE; Set A=its lowest byte
;
DONE:
	LD	A,(DE)	; A=first byte of numeric buffer
	POP	BC	; RESTORE BC

	RET

	END