;              16位二进制数转化为5 BCD码子程序
;********************************************************************
;                  Binary To BCD Conversion Routine
;      This routine converts a 16 Bit binary Number to a 5 Digit
; BCD Number. This routine is useful since PIC16C55 & PIC16C57
; have  two 8 bit ports and one 4 bit port ( total of 5 BCD digits)
;
;       The 16 bit binary number is input in locations H_byte and
; L_byte with the high byte in H_byte.
;       The 5 digit BCD number is returned in R0, R1 and R2 with R0
; containing the MSD in its right most nibble.
;
;   Performance :
;               Program Memory  :       35
;               Clock Cycles    :       885
;
;*******************************************************************;
;
count  equ      16
temp   equ      17
;
H_byte  equ     10
L_byte  equ     11
R0      equ     12              ; RAM Assignments
R1      equ     13
R2      equ     14
;
;其它寄存器自己定义
;
B2_BCD
  bcf     STATUS,0                ; clear the carry bit
	movlw   D'16'
	movwf   count
	clrf    R0
	clrf    R1
	clrf    R2
loop16  
rlf     L_byte
	rlf     H_byte
	rlf     R2
	rlf     R1
	rlf     R0
;
	decfsz  count
	goto    adjDEC
	RETLW   0
;
adjDEC
  movlw   R2
	movwf   FSR
	call    adjBCD
;
	movlw   R1
	movwf   FSR
	call    adjBCD
;
	movlw   R0
	movwf   FSR
	call    adjBCD
;
	goto    loop16
;
adjBCD
  movlw   3
	addwf   0,W
	movwf   temp
	btfsc   temp,3          ; test if result > 7
	movwf   0
	movlw   30
	addwf   0,W
	movwf   temp
	btfsc   temp,7          ; test if result > 7
	movwf   0               ; save as MSD
	RETLW   0
;
;********************************************************************
; 测试程序(注意用法,16位BIN放在H_byte,L_byte;结果放在R0,R1,R2)
;*********************************************************************
main    
movlw   0FF
	movwf   H_byte
	movwf   L_byte          ; The 16 bit binary number = FFFF
	call    B2_BCD          ; After conversion the Decimal Number
;                               ; in R0,R1,R2 = 06,55,35
;
self    goto    self        ;如果不是测试程序,本句无用
;
	org     1FF
	goto    main
;
	END