msCAN: receive-buffer

Started by Sebastian Schuster April 22, 2004
I got a problem in understanding the system of buffers and filters in
the msCAN-modul.
First thing is, when sending a message from the tx-buffer to the
canbus, the same message is written to the receivebuffer. Is the can-
modul sensing the bus and therefore receive its own message?

Secondly, why do I receive all the incoming messages from the canbus
in my receivebuffer (in the debugger all messages appear at the
address of the rx-foreground-buffer), even if I closed the filters. I
thought there is a difference between fore- and backgroundbuffer.
Shouldn't I see only the foregroundbuffer? Regards,

Sebastian



First:
Yes, the modul recieves its own message, but doesn't set
the recieve-Flag!

Second:
Is the recieve-bit set?
"WARNING: To ensure data integrity, do not read the receive buffer registers
while the RXF flag is cleared." (S.524 MC9S12DP256.pdf)

Read the chapter "MSCAN" of the file "MC9S12DP256.pdf" for entire
information. (You can get it from the Motorola-HP.)

Regards,
Christoph

-----Ursprgliche Nachricht-----
Von: Sebastian Schuster [mailto:]
Gesendet: Donnerstag, 22. April 2004 08:51
An:
Betreff: [68HC12] msCAN: receive-buffer I got a problem in understanding the system of buffers and filters in
the msCAN-modul.
First thing is, when sending a message from the tx-buffer to the
canbus, the same message is written to the receivebuffer. Is the can-
modul sensing the bus and therefore receive its own message?

Secondly, why do I receive all the incoming messages from the canbus
in my receivebuffer (in the debugger all messages appear at the
address of the rx-foreground-buffer), even if I closed the filters. I
thought there is a difference between fore- and backgroundbuffer.
Shouldn't I see only the foregroundbuffer? Regards,

Sebastian

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