16open_uadri.txt

在8位单片机中对16位数进行开方运算的汇编子程序

16位整型数开平方
.include "8515def.inc"

         .def   numlo   = r16
         .def   numhi   = r17
         .def   sqrt    = r18
         .def   suber   = r24
         .def   suberh  = r25

; enter with the 16 bit Number in r16,r17
         .org   0x00
         rjmp   reset

         .org   0x20

reset:   ldi    r16,0x02      ; Stack Pointer Setup 
         out    SPH,r16       ; Stack Pointer High Byte 
         ldi    r16,0x5f      ; Stack Pointer Setup 
         out    SPL,r16       ; Stack Pointer Low Byte 
loopm:
         ldi    r16,0x64
         ldi    r17,0x01
         rcall  sqrt
         nop
         rjmp   loopm

Sqrt:
         clr    sqrt
         ldi    suber,1       ; initialize the seed to be subtracted
         clr    suberh        ; for each iteration
 loop:   sub    numlo,suber
         sbc    numhi,suberh
         brlo   exit
         inc    sqrt
         adiw   suber,2       ; keep the number to subtract ODD.
         rjmp loop
 exit: 
         ret                  ; the sqrt(num) on exit is stored in r18