.

16位

整型数开方
 .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

 
.

32位

整型数开方
 ;input r15:r14:r13:r12 (it make a copy from r3::r0)
;output r25:r24
;use r20,r21,r22,r26,r28
;输入返回数据：lsqrt(0x5300164) = 0x2471
;对应于8M晶振时开方所用时间为 48.38us;原程序提供者：Jens NL,Email:jensnl@home.com
.include "8515def.inc"
        .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
; 验证 
;test r25:r24 = lsqrt(0x5300164)
 loopm:
         ldi     r16,0x64
         mov     r12,r16
         ldi     r16,0x01
         mov     r13,r16
         ldi     r16,0x30
         mov     r14,r16
         ldi     r16,0x05
         mov     r15,r16
         rcall   lsqrt
         nop
         rjmp    loopm
         
 lsqrt:
         clr     r20
         clr     r21
         clr     r22
         clr     r24
         clr     r25
         clr     r26
         ldi     r28,16
  m03:
         rol     r15
         rol     r20
         rol     r21
         rol     r22
         rol     r15
         rol     r20
         rol     r21
         rol     r22
         
         lsl     r24
         rol     r25
         rol     r26
         
         cp      r24,r20
         cpc     r25,r21
         cpc     r26,r22
         brsh    m01
         sbc     r20,r24
         sbc     r21,r25
         sbc     r22,r26
         subi    r24,-2
   m05:
   m01:
         dec     r28
         sbrs    r28,0
         sbrc    r28,1
         rjmp    m03
         breq    m08
         mov     r15,r14
         mov     r14,r13
         mov     r13,r12
         rjmp    m03
   m08:
         lsr     r26
         ror     r25
         ror     r24
         ret

 
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