68300

John,

clearly you know what you are doing so there is little chance I
could be much help, but let me try something you did not explicitly
mention.
 All the timing numbers you give suggest everything is working fine
on the 68K part of the system. My experience shows that whenever
there is a wintel part involved, it is a source of problems one
must tackle (this is why I avoid them like the plague...).
What if your DELL system fouls up every once per 1024
or whatever counter there is and sends a too long burst, or something
of that sort?
 Again, this is a very long shot, mostly triggered by my "love" to
wintel systems, but then I believe the hit chances are non-zero.

Dimiter

--------------------------------------------------------------------
Dimiter Popoff
Transgalactic Instruments, Gourko Str. 25 b, 1000 Sofia, Bulgaria
http://transgalactic.freeyellow.com



> To: 68300@yahoogroups.com
> From: "agawam1964" <agawam1964@...>
> Date: Thu, 23 Oct 2003 12:05:07 -0000
> Subject: [68300] TouCAN Dropping Messages
> 
> I have five MC68376 systems communicating with a host PC via CAN 
> using a proprietary protocol.  We're running at 125Kbaud.  One 
> channel is Rx, one channel is Tx.  The Tx we more or less use in a 
> syncronous (polled) mode, with the Tx interrupt basically just 
> clearing the IFLAG register.  The Rx is normal interrupt driven.
> 
> For the most part everything is running smoothly.  Most of the CAN 
> traffic occurs in bursts separated by several seconds, which all five 
> systems weather without incident.  However, the host (Dell XP system) 
> needs to poll one system at a rate of about 10 hz, and every 100 
> seconds or so I'll get the Rx Buffer overrun error on that system.
> 
> I instrumented the ISRs to toggle an I/O pin and found that the Rx 
> ISR is 500 usec.  The Rx ISR where the error is dectected doesn't 
> seem to occur in heavy traffic; typically the prior ISR occurs a few 
> msec before - definately no overlap with prior Rx or Tx ISRs.  
> 
> To help debug this I moved all other ISRs to a lower priority INT, 
> including the heartbeat PIT, with no noticeable effect.  My past 
> experience suggests to me I'm not locking-reading-clearing the 
> buffers and registers correctly, but I've reread the manual about n 
> hundred times and can't see where I'm going wrong.  Is there some 
> subtlety about reading the TouCAN registers and buffers that isn't in 
> the manual?
> 
> --John
>