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

BTW ... !( ( filter ^ messageID_Rx ) is equivalent to the VHDL operatoin 
"filter = messageID_Rx"

--Armin


Dinesh Guleria wrote:
> >> it must be: !( ( filter ^ messageID_Rx ) OR mask );// if ^ means 
> exlusive OR
>
> But where in your VHDL code you are using  ---- exlusiveOR(^) and not 
> (!)operator ...?
>
> On Wed, Dec 5, 2012 at 3:42 PM, Steinhoff <[email protected] 
> <mailto:[email protected]>> wrote:
>
>     Dinesh,
>
>     here is some VHDL code of a CAN core showing the filter process:
>
>        -- Working in basic mode. ID match for standard format (11-bit ID).
>        match <= (((((((CONV_STD_LOGIC(id(3)  = acceptance_code_0(0))
>     OR acceptance_mask_0(0))
>                   AND (CONV_STD_LOGIC(id(4)  = acceptance_code_0(1))
>     OR acceptance_mask_0(1)))
>                   AND (CONV_STD_LOGIC(id(5)  = acceptance_code_0(2))
>     OR acceptance_mask_0(2)))
>                   AND (CONV_STD_LOGIC(id(6)  = acceptance_code_0(3))
>     OR acceptance_mask_0(3)))
>                   AND (CONV_STD_LOGIC(id(7)  = acceptance_code_0(4))
>     OR acceptance_mask_0(4)))
>                   AND (CONV_STD_LOGIC(id(8)  = acceptance_code_0(5))
>     OR acceptance_mask_0(5)))
>                   AND (CONV_STD_LOGIC(id(9)  = acceptance_code_0(6))
>     OR acceptance_mask_0(6)))
>                   AND (CONV_STD_LOGIC(id(10) = acceptance_code_0(7))
>     OR acceptance_mask_0(7)) ;
>
>     The "=" operator means equivalence ...
>
>     --Armin
>
>
>     Dinesh Guleria wrote:
>>     Armin,
>>
>>     >>Isn't it?
>>
>>     The real result must be:-----
>>      !( ( filter ^ messageID_Rx ) & mask );
>>
>>     Above equation is working for me very well many a time i have
>>      used it ..
>>
>>     //Dinesh
>>
>>     On Mon, Dec 3, 2012 at 11:25 PM, Steinhoff
>>     <[email protected] <mailto:[email protected]>> wrote:
>>
>>
>>         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
>>>>
>>>>
>>>
>>
>>
>
>