CRC_CCITT 16-bit assembly language code

Is there someone who has access to the CRC_CCITT 16-bit code written in
ARM7 assembly language?

I'm well aware that there's a ton of code in C for the same.

What's funny is i can do the CRC calculation by hand and have also
developed the algorithm but i'm unable to get the code up and running.

I'd be happy to share the code that i wrote. If you can help me kindly
send me an e-mail at vywack@yahoo.com or we can settle it on this forum.

Thanks a ton

Vy

Vy wrote:
> Is there someone who has access to the CRC_CCITT 16-bit code written in
> ARM7 assembly language?
> 
> I'm well aware that there's a ton of code in C for the same.
> 
> What's funny is i can do the CRC calculation by hand and have also
> developed the algorithm but i'm unable to get the code up and running.

Just a wild-assed guess, are you remembering
to "flush" the crc routine with zeros at the
end?

> I'd be happy to share the code that i wrote. If you can help me kindly
> send me an e-mail at vywack@yahoo.com or we can settle it on this forum.
> 
> Thanks a ton
> 
> Vy

>Vy wrote:
>> Is there someone who has access to the CRC_CCITT 16-bit code written
in
>> ARM7 assembly language?
>> 
>> I'm well aware that there's a ton of code in C for the same.
>> 
>> What's funny is i can do the CRC calculation by hand and have also
>> developed the algorithm but i'm unable to get the code up and running.
>
>Just a wild-assed guess, are you remembering
>to "flush" the crc routine with zeros at the
>end?
>
>> I'd be happy to share the code that i wrote. If you can help me kindly
>> send me an e-mail at vywack@yahoo.com or we can settle it on this
forum.
>> 
>> Thanks a ton
>> 
>> Vy

Here's the detail...for more detail check out the paper by Mr Ross
Williams

The initial value is 0x1d0f
The Poly is 0x1021 which is actually 1 0001 0000 0010 0001
The width is 16 so 16 zeroes are appended to the message 
for example the message is 41h - 0100 0001

      poly=       ------------------------------------------
10001000000100001 ) 1111111111111111010000010000000000000000 

my problem is how do i position the 17 bits (Poly) within a 32 bit
register. Do i keep it at the far right (towards MSB)?

thanks

Vy

On Oct 25, 1:37 am, "Vy" <vyw...@yahoo.com> wrote:
> Is there someone who has access to the CRC_CCITT 16-bit code written in
> ARM7 assembly language?
>
> I'm well aware that there's a ton of code in C for the same.
>
> What's funny is i can do the CRC calculation by hand and have also
> developed the algorithm but i'm unable to get the code up and running.
>

Will the below link help you ?
http://8052.com/codelib/CRC_16.asm

Try looking at the Linux implementation w.r.t this on ARM . I think,
the
ARM CRC routines should be in assembly and they may help you.

Karthik Balaguru

"Vy" <vywack@yahoo.com> wrote in message news:pIKdnXCiGNCbMILanZ2dnUVZ_sytnZ2d@giganews.com...
> Is there someone who has access to the CRC_CCITT 16-bit code written in
> ARM7 assembly language?
>
> I'm well aware that there's a ton of code in C for the same.
>
> What's funny is i can do the CRC calculation by hand and have also
> developed the algorithm but i'm unable to get the code up and running.

How about starting with a working C implementation and optimise it?
After that you will realise that it isn't possible to do any better in assembler...
A good implementation needs about 4-5 instructions for every 8 input bits.

Wilco 

Vy wrote:
> Is there someone who has access to the CRC_CCITT 16-bit code written in
> ARM7 assembly language?
> 
> I'm well aware that there's a ton of code in C for the same.
> 
> What's funny is i can do the CRC calculation by hand and have also
> developed the algorithm but i'm unable to get the code up and running.
> 
> I'd be happy to share the code that i wrote. If you can help me kindly
> send me an e-mail at vywack@yahoo.com or we can settle it on this forum.

1) How does the data come in: a) by octet (byte) or by bit?

2) Study project / homework?

For the CRC_CCITT there are at least 3 ways to implement:

  - 1 bit at a time
  - 4 bits at a time
  - 8 bits (1 byte/octet) at a time

-- 

Tauno Voipio
tauno voipio (at) iki fi

On Wed, 24 Oct 2007 15:37:26 -0500, "Vy" <vywack@yahoo.com> wrote:

>Is there someone who has access to the CRC_CCITT 16-bit code written in
>ARM7 assembly language?
>
>I'm well aware that there's a ton of code in C for the same.
>
>What's funny is i can do the CRC calculation by hand and have also
>developed the algorithm but i'm unable to get the code up and running.
>
>I'd be happy to share the code that i wrote. If you can help me kindly
>send me an e-mail at vywack@yahoo.com or we can settle it on this forum.
>

Here is some ARM assembly code for implimenting CRC-CCITT.
http://homepages.tesco.net/~rainstorm/crc-catalogue.htm

Regards
  Anton Erasmus

>Vy wrote:
>> Is there someone who has access to the CRC_CCITT 16-bit code written
in
>> ARM7 assembly language?
>> 
>> I'm well aware that there's a ton of code in C for the same.
>> 
>> What's funny is i can do the CRC calculation by hand and have also
>> developed the algorithm but i'm unable to get the code up and running.
>> 
>> I'd be happy to share the code that i wrote. If you can help me kindly
>> send me an e-mail at vywack@yahoo.com or we can settle it on this
forum.
>
>1) How does the data come in: a) by octet (byte) or by bit?
>
>2) Study project / homework?
>
>For the CRC_CCITT there are at least 3 ways to implement:
>
>  - 1 bit at a time
>  - 4 bits at a time
>  - 8 bits (1 byte/octet) at a time
>
>-- 
>
>Tauno Voipio
>tauno voipio (at) iki fi
>
>

the data could come in anywhere from a byte to a word (32bits) to several
words. The words are broken down into bytes. The byte is broken down to
bits to feed it to the CRC, check if the topmost bit is 1, if yes XOR it
if not get the next bit in.

i'm working with a Fujitsu MC that uses SPI to talk to the host. An SPI is
a very simple protocol with no CRCs and ACKs but they have added their own
pyrotchnics to included CRC checking and ACK at the end of evey stream of
message.

thanks for the input Tauno

>On Wed, 24 Oct 2007 15:37:26 -0500, "Vy" <vywack@yahoo.com> wrote:
>
>>Is there someone who has access to the CRC_CCITT 16-bit code written in
>>ARM7 assembly language?
>>
>>I'm well aware that there's a ton of code in C for the same.
>>
>>What's funny is i can do the CRC calculation by hand and have also
>>developed the algorithm but i'm unable to get the code up and running.
>>
>>I'd be happy to share the code that i wrote. If you can help me kindly
>>send me an e-mail at vywack@yahoo.com or we can settle it on this
forum.
>>
>
>Here is some ARM assembly code for implimenting CRC-CCITT.
>http://homepages.tesco.net/~rainstorm/crc-catalogue.htm
>
>Regards
>  Anton Erasmus
>
Hi Anton,

I already went through that code. It's not right. I'm using ARM7 and ARM7
does not have instructions like ASL. It only has LSL.
Also the person uses $ signs in front of hex numbers which i can't figure
out why.

Maybe an older version of ARM supported all that but with ARM7 none of
that exists.

THanks Anton

On Fri, 26 Oct 2007 02:27:06 -0500, "Vy" <vywack@yahoo.com> wrote:

>>On Wed, 24 Oct 2007 15:37:26 -0500, "Vy" <vywack@yahoo.com> wrote:
>>
>>>Is there someone who has access to the CRC_CCITT 16-bit code written in
>>>ARM7 assembly language?
>>>
>>>I'm well aware that there's a ton of code in C for the same.
>>>
>>>What's funny is i can do the CRC calculation by hand and have also
>>>developed the algorithm but i'm unable to get the code up and running.
>>>
>>>I'd be happy to share the code that i wrote. If you can help me kindly
>>>send me an e-mail at vywack@yahoo.com or we can settle it on this
>forum.
>>>
>>
>>Here is some ARM assembly code for implimenting CRC-CCITT.
>>http://homepages.tesco.net/~rainstorm/crc-catalogue.htm
>>
>>Regards
>>  Anton Erasmus
>>
>Hi Anton,
>
>I already went through that code. It's not right. I'm using ARM7 and ARM7
>does not have instructions like ASL. It only has LSL.
>Also the person uses $ signs in front of hex numbers which i can't figure
>out why.
>
>Maybe an older version of ARM supported all that but with ARM7 none of
>that exists.

LSL and ASL are the same thing. The assembler used, probably has a few
pseudo instructions to help with readability.

Regards
  Anton Erasmus