> I have 4 circuits with on each of them exists PIC18F258.these are
slaves.and
> there is 1 master PIC18F458  as master.
> They talk by can bus.I send messages with the can_msg_id = id  of
the slave
> circuit.
> for example slave 1  =1
>                  slave 2 = 2
>                  slave 3 = 3
> so a slave doesnt take a msgs to its reveice buffer if that msgs
doesnt
> belong to it.
>
> In order to achieve this , i must use can mask registers.
>
> has anyone  wrote sth like this or any knowledge about it?
> thanks...

I'm writing code for those PICs. Maybe I can help you, but you should
be more specific explaining what you want to know. Anyway, I'll try to
answer...

Let's say you're using RX buffer 0. You have one mask and two filters
associated with that buffer, right? When a message is received it's ID
is compared against the filters. If any matches, the received message
is placed in the receive buffer. BUT only the bits in the mask set to
'1' will be checked (e.g. MASK=000...000 -> all messages will be
received, regardless of filter values; MASK=000...010 -> only messages
with 2nd ID bit equal to filter1's 2nd bit OR filter2's 2nd bit will
be accepted; MASK=111...111 -> All messages equal to ANY filter will
pass).

 If you just want messages with ID=x to be received, you set the two
filters to 'x' and the mask register to all 1's.

Is this what you wanted to know?

You might find useful CAN routines in C to start with in AN738 at
http://www.microchip.com/1010/suppdoc/appnote/all/an738/index.htm

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