sqr16.asm

Find out 16 bit number square root. Asm51 source

;+-----------------------------------------------------------------+
;| Purpose: Find out the square root of the 16-bit number          |
;| 8-Bit version by Joao Dartagnan Antunes Oliveira (04/20/1993)   |
;| 16-Bit modification by Bruno Marcio Diogo Venancio (08/10/2007) |
;| Email: [e-mail]                                  |
;| Brazil                                                     v1.1 |
;| Input: B (MSB) and A (LSB)   (binary)                           |
;| Output: A                                                       |
;| Destroy : R2,R3,R4,R5,R6,R7                                     |
;|       THIS CODE CAN BE FREELY DISTRIBUTED WITHOUT CHANGES       |
;+-----------------------------------------------------------------+
;

COUNT_L EQU  R2
COUNT_H EQU  R3
ACC_L   EQU  R4
ACC_H   EQU  R5

X_L     EQU  R6
X_H     EQU  R7


        ORG 0

;
;Test Routine
;
LOOP:
        mov a,#low(25)
        mov b,#high(25)

        call SQRTBI          ; SQRT(40000)=200



        sjmp $

;
; METHOD:
;
; Add in one accumulator an odd number counter until it cotains a value great or
; equal than X , at this moment, the counter value divided for 2 will be SQRT(X)
;

SQRTBI:

	mov X_L,a
	mov X_H,b

	mov COUNT_L,#1	        ;COUNTER <- 1
	mov COUNT_H,#0

	mov ACC_L,#0    	;ACUMULATOR <- 0
	mov ACC_H,#0

sqrtbi00:
	clr c
	mov a,ACC_L     	;ACUMULATOR >= X ?
	subb a,X_L

        mov a,ACC_H
	subb a,X_H

	jnc sqrtbi01	        ;IF YES, END

        clr C
        mov a,COUNT_L
        add a,#2                ;COUNTER <- COUNTER + 2
        mov COUNT_L,a

        mov a,COUNT_H
        addc a,#0
        mov COUNT_H,a


        clr C                  ;Sum odd numbers count
        mov a,ACC_L
        add a,COUNT_L
        mov ACC_L,a

        mov a,ACC_H
        addc a,COUNT_H
        mov ACC_H,a

	sjmp sqrtbi00

sqrtbi01:

        clr C

        mov a,COUNT_H            ;COUNTER /2 = SQRT(X)
        rrc a

        mov a,COUNT_L
        rrc a

	ret


        END