TouCAN: abort transmission

Hello All

Does anyone know a cleaner way to abort a pending or active TouCAN
transmission than just writing 0b1000="NOT Ready For Transmit" to the
Control/Status register CODE field?  

I'm concerned about some frame being aborted in mid-transmission,
causing a stuff error, adding error frames to an already heavily-loaded
bus.  Thanks in advance!

BACKGROUND:

I need to abort and delete any TouCAN msg that has failed to be sent
successfully after 10 ms or more of waiting for bus arbitration or an
ACK.  (We don't want to send stale data even during powerup, power-loss
recovery or bursts of too-heavy bus loading.)

The usual case would be that no other node was powered up and ACKing.
Occasionally the mechanism will be responding to a failure to gain bus
access (100% bus load by high-priority msgs).  I want to minimize the
risk of interrupting a partial frame.


In other words, a TouCAN msg has already been written into a mailbox
("Message Buffer"), and enabled for transmission.  I already wrote
0b1100="Data Frame to be Transmitted Once" into Control/Status register
CODE field) - i.e. Section 16.3. That mailbox might or might not have
been copied to the shift register, might be waiting for arbitration to
give it access, might be transmitting for the first time, or
re-transmitting due to lack of ACK.

I need to step on a mailbox that is live without causing a glitch.  


I've read section 16.4.3, "Transmit Process" and the following, but they
seem to only address  _orderly_  deactivation, turning off a mailbox
that is not loaded.  I've loaded the mailbox and pulled the trigger, but
got a hangfire.

16.3.1.5 Message Buffer Activation/Deactivation Mechanism
A buffer is deactivated by writing the appropriate deactivation code to
the control/status word for that
buffer. A buffer is typically deactivated to reconfigure the buffer (for
example to change the buffer's
function from Rx to Tx or Tx to Rx).

With some CAN controllers, there is a bit to set somewhere that waits
for the next inter-frame gap, and THEN deactivates a TX mailbox.  Does
anyone know of a mechanism like that in TouCAN?

Rick Corey  



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