PIC18F dividing in assembly language

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Raju C

Joined: 17 Sep 2009
Posts: 43
Location: Bangalore

23 Oct 2009 7:15 PIC18F assembly

Hi all..
can anybody tell me how to do the program for INT(3E85h/1024) in assembly , i am using PIC18F and here no division operation so pls can any one help .. how to write code ?

betwixt

Joined: 04 Jul 2009
Posts: 383
Helped: 62
Location: Wales, UK

23 Oct 2009 9:08 Re: PIC18F assembly

1024 = 2^10 so shift it right 10 times. (hint: RRF)

Brian.

Raju C

Joined: 17 Sep 2009
Posts: 43
Location: Bangalore

23 Oct 2009 10:04 Re: PIC18F assembly

ya i got .. whether i can use RRf in program directly ? their is no instruction such ?

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wp100

Joined: 15 May 2009
Posts: 324
Helped: 45
Location: England

23 Oct 2009 10:13 Re: PIC18F assembly

hi,

RRF on the 16F

RRCF or RRNCF on the 18F

Raju C

Joined: 17 Sep 2009
Posts: 43
Location: Bangalore

23 Oct 2009 11:39 PIC18F assembly

ya correct .. RRCF in 18F but .. if you use this you wont get the result for all no's .. see 3E85 and 3F4d you check this operation on both output should be 15 but we wont get that..

ravimarcus

Joined: 09 May 2005
Posts: 204
Helped: 19
Location: Bangalore, INDIA

23 Oct 2009 13:07 Re: PIC18F assembly

Raju C wrote:

ya correct .. RRCF in 18F but .. if you use this you wont get the result for all no's .. see 3E85 and 3F4d you check this operation on both output should be 15 but we wont get that..

Thats because you are not clearing the carry while looping back.

Try this code.

movlw 3Fh
movwf msb
movlw 4Dh
movwf lsb

movlw .10
movwf counter

loop bcf status,carry ; carry is cleared while looping back
rrcf msb,same
rrcf lsb,same
decfsz counter,same
goto loop

Cheers

Ravi

Raju C

Joined: 17 Sep 2009
Posts: 43
Location: Bangalore

26 Oct 2009 5:19 PIC18F assembly

same means here you are telling two times shift ?after shifting msb i need to clear carry .. and again after shifting lsb also i have to clear carry ??

ravimarcus

Joined: 09 May 2005
Posts: 204
Helped: 19
Location: Bangalore, INDIA

26 Oct 2009 5:26 Re: PIC18F assembly

Raju C wrote:

same means here you are telling two times shift ?after shifting msb i need to clear carry .. and again after shifting lsb also i have to clear carry ??

same = 1, means save it back in the same register. ex:- rrf msb,1.

Before shifting MSB, clear the carry, any carry from MSB has to be shifted into LSB. So for the next looping, clear the carry if any from LSB as we do not need it.

Cheers

Ravi

Raju C

Joined: 17 Sep 2009
Posts: 43
Location: Bangalore

26 Oct 2009 7:52 PIC18F assembly

ya 1 means it will store to same reg , i will try this and if i get any prob i will ask you ..

sajal1975

Joined: 25 Mar 2005
Posts: 150
Helped: 3

26 Oct 2009 11:09 Re: PIC18F assembly

WRITIN SOFTWARE IS NT A JOKE.

Raju C

Joined: 17 Sep 2009
Posts: 43
Location: Bangalore

27 Oct 2009 9:28 Re: PIC18F assembly

sajal1975 wrote:

WRITIN SOFTWARE IS NT A JOKE.

ya its not a joke ??

Added after 2 hours 31 minutes:

ravimarcus wrote:

Raju C wrote:

same means here you are telling two times shift ?after shifting msb i need to clear carry .. and again after shifting lsb also i have to clear carry ??

i tried it but after shifting 10 times we will get 1F and 26 in MSB and in LSB respectively.. but the result should be F so where it will be??