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

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

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
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>