Re: Re: CAN Mask & Filter setting at ---- software level

Dinesh.

the result should be:

result = ( filter XOR id ) OR mask;

Acceptance happens  if all bits are set in result.

Regards

--Armin

PS: SJA1000 spec / p. 45

Dinesh Guleria wrote:
> Got the concept.
>
> Now if i want DM to trigger for following types 0x01 & 0x33 :--
>
> Type to be accepted :--
> 0x01;                // 0000 0001
> 0x33;                // 0011 0011
>
> mask = 0xCD;   // 1100 1101                        -----> put 0 for 
> diffrent bits ------ & ------ 1 for common bits
> filter = 0x01;      // 0000 0001 ------>put 0 for dont care bits 
> ------ & ------ SAME VALUE for common bits
>
> result = ( ( filter ^ a_ ) & mask );
> if(!result)
> {
>      //accept
> }
>
>
> This will Rx 0x001, 0x003, 0x011, 0x013, 0x021, 0x023, 0x031 and 0x033 
> IDs.
>
> Still in terms of CAN Rx workload for the processor, only 6 unwanted 
> IDs out of a possible total 2032 CAN IDs (for 11 bit IDEs) to Rx may 
> be of some reduced workload benefit.
>
> We can put further filtering at the next level of software to accept 
> message what we want.
>
> BTW, weonly get 2032 and not 2048 11 bit CAN IDs because no IDs are 
> allowed to have all 7 most significant bits set at the same time.
>
> Regards,
> Dinesh
>
>
> On Sat, Dec 1, 2012 at 9:34 PM, Dinesh Guleria <[email protected] 
> <mailto:[email protected]>> wrote:
>
>     Hi,
>
>     I have enable my can controller to receive all messages & trying
>     to filtering messages it at software level.
>     I referred following link by Heikki
>     http://old.nabble.com/Setting-CAN-MASK---ID-registers-td14881913.html
>
>     Suppose i want to receive only ID_1 & ID_2.
>     But I was not able to get the desired result ID-0x03 is still
>     passing the software filter
>
>
>     ID_1  =  0x01;       // 0000 0001
>     ID_2  =  0x33;       // 0011 0011
>     mask = 0x32;       // 0011 0010
>     filter =    0x01;       // 0000 0001
>
>     if  ----  messageID_Rx  =  0x03
>
>     ==========  CODE ======================
>
>     result = !( ( filter ^ messageID_Rx ) & mask );
>
>     if ( result )
>     {
>           // ID accepted
>     }
>
>
>     ====================================
>
>     Can someone on list help me to correct this. Or can suggest me
>     where i am getting wrong ?
>     Any reply will be appreciable.
>
>     Thanks & Regards,
>
>     Dinesh
>
>