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

>>Well ... you are right ... the CAN controller does it wrong :)
Means Got confused with your statement ....???

Do you agree with mine ?

I have just checked under debugger your equation is giving result of zero
for almost all ID.
result = !( ( filtr ^ a_ ) | mask );


This equation only pass right ID
result = !( ( filtr ^ a_ ) & mask );
This will Rx 0x001, 0x003, 0x011, 0x013, 0x021, 0x023, 0x031 and 0x033 IDs.

On Thu, Dec 6, 2012 at 2:46 PM, Steinhoff <[email protected]> wrote:

>  Dinesh Guleria wrote:
>
> How you are setting class or mask bit ?
>
>
>  ??
>
>
>
>  In my case :--
>
>  ID_1  =  0x01;       // 0000 0001
> ID_2  =  0x33;       // 0011 0011
> mask = 0x32;       // 0011 0010
> -------------------------------------> 0 for common bits, ------ where bits
> are different put bit as 1 -- for dont care
> filter =    0x01;       // 0000 0001
> ------------------------------------->  copy common bits to the filter &
> dont care for the diffrent bits
>
>
> ??  Well ... you are right ... the CAN controller does it wrong :)
>
>
>
>
> On Wed, Dec 5, 2012 at 11:18 PM, Steinhoff <[email protected]> wrote:
>
>>
>> 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  ----  exlusive OR(^) and not
>> (!)operator ...?
>>
>> On Wed, Dec 5, 2012 at 3:42 PM, Steinhoff <[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]>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]>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
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>
>