# SXMicrocontrollerMathMethod

## 12 Bit Square Root

### by Nikolai Golovchenko

```;**********************************************************************
;by Nikolai Golovchenko
;12 bit SQARE ROOT
;Input:
;ACCB0 - high byte
;ACCB1 - low byte
;Result:
;ACCB0 - 6bit
;Used:
;TEMPB0 - temporary for result
;TEMPB1 - temporary for input
;LOOPCNT - counter
;Memory used
;32 instructions
;5 RAM bytes
;11+18*6-2+7= 124 cycles all cases
;**********************************************************************
Sqrt12  clr     TEMPB0          ;clear all used
clr     TEMPB1          ;temporary registers
mov     W, #6           ;and setup counter
mov     LOOPCNT, W      ;

swap    ACCB0           ;Left justify
mov     W, <>ACCB1      ;12bit value
and     W, #\$0f         ;in two byte
or      ACCB0, W        ;accumulator
mov     W, <>ACCB1      ;
and     W, #\$f0         ;
mov     ACCB1, W        ;
Sqrt12a
rl      ACCB1           ;shift next
rl      ACCB0           ;two higher bits
rl      TEMPB1          ;of input
rl      ACCB1           ;to
rl      ACCB0           ;TEMPB1
rl      TEMPB1          ;

mov     W, #\$01         ;take current result (shifted 2 bits left)
add     W, TEMPB0       ;and OR with 01 (test bit) - add clears C
rl      TEMPB0          ;and reserve place for the next bit

mov     W, TEMPB1-w     ;test substraction for borrow
snb     C
setb    TEMPB0.2        ;set next result bit if no borrow
snb     C
mov     TEMPB1, W       ;store substraction result if no borrow

decsz   LOOPCNT         ;repeat untill all 6 bits will be found
jmp     Sqrt12a

clrb    C
rr      TEMPB0          ;right
mov     W, >>TEMPB0     ;justify the result
mov     ACCB0, W        ;and copy to result register
ret
;**********************************************************************
;Last updated 16Nov99
```

 file: /Techref/scenix/lib/math/sqrt/sqrt12_sx.htm, 2KB, , updated: 2004/6/10 13:40, local time: 2019/12/16 03:07, owner: NG--944, TOP NEW HELP FIND:  3.94.200.93:LOG IN

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