;
;****************************************************************************
;
;  Purpose:
;	Conversion from 2 digit HEX to binary
;	
;
;  Date:
;	08/03/99
;
;  Author:
;	Umar Tsani Abdurrahman (utsania@yahoo.com)
;
;  Modifications:
;	
;
;  Processor:
;	Generic 8051
;
;  Assembler:
;	ASM51
;
;  Dependencies:
;	None
;
;  Files:
;	None
;
;  Philosophic:
; 
;****************************************************************************
;	Free usage without modification 
;****************************************************************************
;  Description:
;	Converts Hex string to binary 
;
;  Entry Requirements:
;	Acc contains LSB digit to convert 
;	B Contains MSB digit to convert
;	(all DIGITS IN CAPITAL:0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F)
;  On Exit:
;	A contains Conversion Result Binary Value
;
; Usage Example:
; convert hex value : 5A (HEX) to binary
; Mov 	a,#'A' ;LSB
; mov 	b,#'5'  ;MSB
; lcall	hex2bin
;
; the result in A is 'Z' (binary)
; 
hex2bin:			;lsb part, this process subtract the value so LSB will reflect binary value of LSB digit
		subb	a,#'0'	
		cjne	a,#9+1,h2bkc1
h2bkc1:		jc	h2bkc2
		subb	a,#7
h2bkc2:		clr	c
		push	acc	;put the result on stack
		
		mov	a,b	;do the MSB part
				;msb part 
		subb	a,#'0' 
		cjne	a,#9+1,h2bkc3
h2bkc3:		jc	h2bkc4
		subb	a,#7
h2bkc4:		clr	c		
		mov	b,#010h	;16 times the result is the MSB
		mul	ab
		
		
		mov	b,a	;Put the result on B 
		pop	acc	;put back LSB
		add	a,b	;lsb+msb
				;result on a
		ret