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

Well,

that what the SJA1000 specification is showing by the "aceptance 
schemes" with the
logical gates is not correct ... there seems to be a misinterpretation 
of the IEC gate symbol "=" :)

The real result must be:

result = NOT( filter XOR id ) OR mask;

Isn't it?

--Armin


Steinhoff wrote:
>
> 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
>>
>>
>