From: Tony Nixon
; ------------------------------------------
; SUBROUTINE - 24 BIT DIVISION
; numerator: nratorH nratorM nratorL
; denominator: denomH denomM denomL
;
; result: nratorH nratorM nratorL
; remainder: remainH remainM remainL
;
divizn movlw .24
movwf BCount
movf nratorH,w
movwf shiftH
movf nratorM,w
movwf shiftM
movf nratorL,w
movwf shiftL
clrf nratorH
clrf nratorM
clrf nratorL
;
clrf remainH
clrf remainM
clrf remainL
dloop bcf status,carry
rlf shiftL
rlf shiftM
rlf shiftH
rlf remainL
rlf remainM
rlf remainH
movf denomH,w
subwf remainH,w
btfss status,z
goto nochk
;
movf denomM,w
subwf remainM,w
btfss status,z
goto nochk
;
movf denomL,w
subwf remainL,w
nochk btfss status,carry
goto nogo
;
movf denomL,w
subwf remainL
btfss status,carry
decf remainM
movf remainM,w
xorlw 0xff
btfsc status,z
decf remainH
movf denomM,w
subwf remainM
btfss status,carry
decf remainH
movf denomH,w
subwf remainH
bsf status,carry
nogo rlf nratorL
rlf nratorM
rlf nratorH
decfsz BCount
goto dloop
;
return
Thanks Fred... I posted your version under Tony's...
I wish I had time to test and debug all the code on the site, but I simply
can't.. I depend on people like you who find problems, fix them and share
the result.
In short: THANK YOU! <GRIN>
---
James Newton, webhost piclist.com (former Admin #3)
jamesnewton at piclist,com 1-619-652-0593 fax:1-208-279-8767
PIC/PICList FAQ: http://www.piclist.com or .org
-----Original Message-----
From: Fred Maher [mailto: FREDFMAH at terra,es]
Sent: Saturday, September 28, 2002 10:59 PM
To: webmaster at piclist,com
Subject: I need someone to help me with:24/24
Dear webmaster,
Looking for a routine that works.....
In the PIC list , the only one I could get working and that produced a
useable result was Tony Nixons....
Even so it needed tweaking
First compile with MPLAB gave more than 30 errors plus warnings.
1 Things not defined initially
2 default warnings
3 Errors like status should be STATUS
These are the things that leave us newbies on the floor.
Having said all this this code is quite quick and the ONLY ONE that is easy
to get working in the PICLIST !!!!!!!!!!!!!!
The tweaked code follows:---------------------------------------
;---------------------------------------------------------------------
;------- HEADER ----------
;---------------------------------------------------------------------
; FredMaher Madrid 30 Sept 02 fredfmah@terra.es
; Tony Newton's 24÷24 routine with worked example
; LCD MESSAGES
; position at beginning of 1st line col 0 movlw H'80
; position at beginning of second line movlw H'C0'
LIST P=16F628 ; 16F628 Runs at 20 MHz
INCLUDE "p16F628.inc"
__CONFIG _CP_OFF & _WDT_OFF & _HS_OSC & _PWRTE_ON & _LVP_OFF &
_BODEN_OFF
ERRORLEVEL -224 ; suppress annoying message because of tris
ERRORLEVEL -302 ; suppress message because of page change
;__FUSES _PWRTE_ON & _CP_OFF & _WDT_ON & _HS_OSC & _LVP_OFF & _MCLRE_OFF
& _BODEN_OFF
; Define Information
#DEFINE RS PORTA, 2
#DEFINE E PORTA, 3
;#DEFINE TOGGLESW PORTB, 6 ; not used at the moment
;#DEFINE LED PORTB, 5
; Macro
Bank0 macro
bcf STATUS, RP0 ;Select memory bank 0
bcf STATUS, RP1
endm
Bank1 macro
bsf STATUS, RP0 ;Select memory bank 1
bcf STATUS, RP1
endm
;---------------------------------------------------------------
CBLOCK 20H ; from 20C to 7F = 67 ;Note. Careful with memory
pages
; until you get some
practice.
;---------------------------------------------------------------
; MATH ROUTINES
; 24 / 24 Div --> 24
; TONY NIXON's Algorithm starts here + my retouching
; SUBROUTINE - 24 BIT DIVISION
; numerator: nratorH nratorM nratorL
; denominator: denomH denomM denomL
;
; result: nratorH nratorM nratorL
; remainder: remainH remainM remainL
nratorH
nratorM
nratorL
denomH
denomM
denomL
remainH
remainM
remainL
shiftH
shiftM
shiftL
BCount
;-------------------------------------------------------------------
ENDC ; end of definition block
;-------------------------------------------------------------------
ORG 0 ; start at location 0
goto Main ; jump over to main routine
Main:
call Div24
Homesweethome:
nop
goto Homesweethome
Div24:
; Example 1000000/16960 = F4240 / 4240 =58.962 ( remainder...
remain/denom gives the decimal correctly... = Dec 0.962)
movlw 0x0F ; using Tony's notation
movwf nratorH
movlw 0x42
movwf nratorM
movlw 0x40
movwf nratorL
movlw 0x00
movwf denomH
movlw 0x42
movwf denomM
movlw 0x40
movwf denomL
divizn movlw .24
movwf BCount
movf nratorH,w
movwf shiftH
movf nratorM,w
movwf shiftM
movf nratorL,w
movwf shiftL
clrf nratorH
clrf nratorM
clrf nratorL
;
clrf remainH
clrf remainM
clrf remainL
dloop bcf STATUS,C
rlf shiftL,f
rlf shiftM,f
rlf shiftH,f
rlf remainL,f
rlf remainM,f
rlf remainH,f
movf denomH,w
subwf remainH,w
btfss STATUS,Z
goto nochk
;
movf denomM,w
subwf remainM,w
btfss STATUS,Z
goto nochk
;
movf denomL,w
subwf remainL,w
nochk btfss STATUS,C
goto nogo
;
movf denomL,w
subwf remainL,f
btfss STATUS,C
decf remainM,f
movf remainM,w
xorlw 0xff
btfsc STATUS,Z
decf remainH,f
movf denomM,w
subwf remainM,f
btfss STATUS,C
decf remainH,f
movf denomH,w
subwf remainH,f
bsf STATUS,C
nogo:
rlf nratorL,f
rlf nratorM,f
rlf nratorH,f
decfsz BCount,f
goto dloop
;
Return
end
;---------------------------------------------------------------------------------------------------------------------------------
; End of 24/24 division routine by Tony Nixon
;----------------------------------------------------------------------------------------------------------------------------------
Cheers
Fred Maher
Madrid Spain
Code:
Correcting High byte remainder error and added comments to Tony Nixon Code and Fred Mahers update to the 24bit by 24bit divide routine. Thank you all for the USEFUL Code references and comments here. note Nikolai Golovchenko and Zet P.
Fred Finster 3/15/2005 Error Corrected
Numerator Denominator Remainder Answer Divisor Remainder
FFFFFF FFFFFE FF0001 000001 FFFFFE 000001
8FFFFF 8FFFFE FF0001 000001 8FFFFE 000001
2FFFFF 2FFFFE FF0001 000001 2FFFFE 000001
2FFFFE 2FFFFE 000001 2FFFFE 000000
2FFFFD 2FFFFE 000000 2FFFFE 2FFFFD
0F4240 004240 00003A 004240 003FC0
;-----------------------------------------------------
; Here is the changed code, that corrects the HIGH byte remainder error
; btfsc STATUS, C ; Carry Set? Then execute fixup code for when a borrow is generated
; goto nodec_remainM ; when no borrow bit is needed from the higher byte positions.
;
;
;--------------------------------------------------------------------
; SUBROUTINE - 24 BIT DIVISION from TONY NIXON
; numerator: nratorH nratorM nratorL
; denominator: denomH denomM denomL
;
; result: nratorH nratorM nratorL
; remainder: remainH remainM remainL
;
Divide_24x24:
movlw .24 ; set decimal 24 loop count
movwf BCount
movf nratorH,w ; copy Numerator into Shift Holding ram registers
movwf shiftH
movf nratorM,w
movwf shiftM
movf nratorL,w
movwf shiftL
clrf nratorH ; clear final Answer Numerator Ram locations
clrf nratorM
clrf nratorL
;
clrf remainH ; clear final Answer Remainder Ram locations
clrf remainM
clrf remainL
dloop:
bcf STATUS, C ; bit clear Carry Flag in STATUS register
rlf shiftL, f ; Shift numerator(dividend) Left to move
rlf shiftM, f ; next bit to remainder
rlf shiftH, f ; and shift in next bit of result
rlf remainL, f ; shift carry (next Dividend bit) into remainder
rlf remainM, f
rlf remainH, f
movf denomH,w
subwf remainH,w ; subtract divsor(denomH) from(newly shifted left) Remainder HIGH byte.
btfss STATUS, Z
goto nochk ; skip if result was ZERO from good subtraction result
;
movf denomM,w
subwf remainM,w ; subtract divsor(denomM) from(newly shifted left) Remainder MIDDLE byte.
btfss STATUS, Z
goto nochk ; skip if result was ZERO from good subtraction result
;
movf denomL,w
subwf remainL,w ; subtract divsor(denomL) from(newly shifted left) Remainder LOW byte.
nochk:
btfss STATUS, C ; Carry SET? then denom is larger than reemainder
goto nogo
;
movf denomL,w
subwf remainL, f ; Subtract denominator from remainder value in Low Byte
btfsc STATUS, C ; Carry Set? Then execute fixup code for when a borrow is generated
goto nodec_remainM ; when no borrow bit is needed from the higher byte positions.
decf remainM, f ; Decrement to Borrow from Middle Byte, because carry was SET.
movf remainM,w
xorlw 0xff ; Check if rollover from Borrow occurred. remainM value went from 0 to 0xFF
btfsc STATUS, Z
decf remainH, f ; ZERO bit set, yes rollover, so Decrement to Borrow from High Byte, too!
nodec_remainM:
movf denomM,w
subwf remainM, f ; Subtract denominator from remainder value in Middle Byte
btfss STATUS, C
decf remainH ,f ; Decrement High Byte, to borrow 1 bit
movf denomH,w
subwf remainH, f ; Subtract denominator from remainder value in High Byte
bsf STATUS, C ; set CARRY bit to rotate in Numerator Result next.
nogo:
rlf nratorL, f ; rotate Numerator result left 1 bit
rlf nratorM, f
rlf nratorH, f
decfsz BCount, f ; decrement the Loop Bit Counter
goto dloop
;
return ; all done
+
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