One of my favorite compromise parity checkers was
originally implemented in hardware and published
in electronics design. In the original the ac was declared as
an accumulator it can be replaced as a local variable.

If you use this any public way credit the sources.

It is a clever algorithm

w..

int parity(char ch)
  {
   /*
     Implemented in C Based on the original
     hardware implementation in Electronics design.
     Walter Banks Byte Craft Limited
     September 1991

     Electonics Design Aug 22, 1991
      Noor Singh Khalsa
      EG&G
      P.O Box 809,
      MS E-1, Los Alamos, NM 87544
      (505) 667-0200
    */

   ch = (ch >> 1) ^ ch ;
   return (((ac = (((ch >> 2) ^ ch)) & 0x11) == 0) ? 1 : ((ac ^ 0x11) == 0) );
   if ((ch = (((ch >> 2) ^ ch)) & 0x11) == 0) return 1;
   if ((ch ^ 0x11) == 0) return 1;
   return 0;
  }



Brian Millward wrote:

> I am fairly new to PIC programming and I am building a radio clock to decode
> Rugby MSF transmissions.
>
>
>
> It all works, but I have not done any parity checking.
>
>
>
> I have some BCD variables and a checksum bit and I need to check that all
> the bits add up to an odd number.
>
>
>
> I have thought of checking the lsb, then shifting right and repeating etc,
> adding all the bits together, but I am sure that there is an easier way I
> just cannot think of it
>
>
>
> Apologies for seeming to be a bit dense, but I am trying to master it.
>
>
>
> By the way, I am using CCS 'C' compiler.
>
>
>
> Thanks for any help you may be able to give.
>
>
>
> Regards ... Brian
>
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