Mege16 AVR单片机实现中的BCD码转换与运算

.org $0000
rjmp RESET

;***以下是16位2进制（fbinH:fbinL）码转换成BCD码（tBCD2:tBCD1:tBCD0）程序***
.equ AtBCD0 =13  ;address of tBCD0
.equ AtBCD2 =15  ;address of tBCD1

.def tBCD0 =r13  ;BCD value digits 1 and 0
.def tBCD1 =r14  ;BCD value digits 3 and 2
.def tBCD2 =r15  ;BCD value digit 4
.def fbinL =r16  ;binary value Low byte
.def fbinH =r17  ;binary value High byte
.def cnt16a =r18  ;loop counter
.def tmp16a =r19  ;temporary value
bin2BCD16:
 ldi cnt16a,16 ;Init loop counter 
 clr tBCD2  ;clear result (3 bytes)
 clr tBCD1  
 clr tBCD0  
 clr ZH  ;clear ZH (not needed for AT90Sxx0x)
bBCDx_1:lsl fbinL  ;shift input value
 rol fbinH  ;through all bytes
 rol tBCD0  ;
 rol tBCD1
 rol tBCD2
 dec cnt16a  ;decrement loop counter
 brne bBCDx_2  ;if counter not zero
 ret   ;   return
bBCDx_2:ldi r30,AtBCD2+1 ;Z points to result MSB + 1
bBCDx_3:
 ld tmp16a,-Z ;get (Z) with pre-decrement
subi tmp16a,-$03 ;add 0x03
 sbrc tmp16a,3 ;if bit 3 not clear
 st Z,tmp16a ; store back
 ld tmp16a,Z ;get (Z)
 subi tmp16a,-$30 ;add 0x30
 sbrc tmp16a,7 ;if bit 7 not clear
 st Z,tmp16a ; store back
 cpi ZL,AtBCD0 ;done all three?
 brne bBCDx_3  ;loop again if not
 rjmp bBCDx_1
 
  
;***8位2进制(fbin)转换成BCD码(tBCDH:tBCDL)程序***
.def fbin =r16  ;8-bit binary value
.def tBCDL =r16  ;BCD result MSD
.def tBCDH =r17  ;BCD result LSD
bin2bcd8:
 clr tBCDH  ;clear result MSD
bBCD8_1:subi fbin,10  ;input = input - 10
 brcs bBCD8_2  ;abort if carry set
 inc tBCDH  ;inc MSD
 rjmp bBCD8_1  ;loop again
bBCD8_2:subi fbin,-10 ;compensate extra subtraction
ret

;***BCD码(fBCD2:fBCD1:fBCD0)转换成16位2进制（tbinH:tbinL）程序***
.def copyL =r12  ;temporary register
.def copyH =r13  ;temporary register
.def mp10L =r14  :Low byte of number to be multiplied by 10
.def mp10H =r15  ;High byte of number to be multiplied by 10
.def adder =r19  ;value to add after multiplication 
mul10a: ;***** multiplies "mp10H:mp10L" with 10 and adds "adder" high nibble 
 swap adder
mul10b: ;***** multiplies "mp10H:mp10L" with 10 and adds "adder" low nibble 
 mov copyL,mp10L ;make copy
 mov copyH,mp10H
 lsl mp10L  ;multiply original by 2
 rol mp10H
 lsl copyL  ;multiply copy by 2
 rol copyH  
 lsl copyL  ;multiply copy by 2 (4)
 rol copyH  
 lsl copyL  ;multiply copy by 2 (8)
 rol copyH  
 add mp10L,copyL ;add copy to original
 adc mp10H,copyH 
 andi adder,0x0f ;mask away upper nibble of adder
 add mp10L,adder ;add lower nibble of adder
 brcc m10_1  ;if carry not cleared
 inc mp10H  ; inc high byte
m10_1: ret 

;*********************************************************
.def tbinL =r14  ;Low byte of binary result (same as mp10L)
.def tbinH =r15  ;High byte of binary result (same as mp10H)
.def fBCD0 =r16  ;BCD value digits 1 and 0
.def fBCD1 =r17  ;BCD value digits 2 and 3
.def fBCD2 =r18  ;BCD value digit 5
BCD2bin16:
 andi fBCD2,0x0f ;mask away upper nibble of fBCD2
 clr mp10H  
 mov mp10L,fBCD2 ;mp10H:mp10L = a
 mov adder,fBCD1
 rcall mu