RE: Bus Off recovery in TouCAN / FlexCAN: automatic?

I'm not quite sure exactly what you're asking.
 
The errata is saying that the automatic bus off recovery mechanism (128
sequecnies of 11 recessive bits) doesn't quite meet the ISO description
since ISO says that the node should remain inactive until user
intervention, i.e. CPU software, enables it.  Some versions of
Toucan/Flexcan will automatically enable after 128 sequencies WITHOUT
s/w intervention and therefore do not strictly meet the ISO spec.  It
will still generate an optional interrupt if enabled.
 
On more recent devices including MPC5554, there is a new control bit,
BOFFREC, that can enable or disable the automatic enabling portion, but
still forces the can to wait 128 sequencies.
 
565 rev D, I'm almost certain there is no BOFFREC control bit which
means bus off recovery is always automatic which means the errata
applies i.e. follow the workaround if you have to follow the ISO spec
which says "until user intervention".
 
- Allan

________________________________

From: [email protected] [mailto:[email protected]] On Behalf
Of Corey, Richard
Sent: Friday, March 16, 2007 4:59 PM
To: [email protected]
Subject: [MPC500] Bus Off recovery in TouCAN / FlexCAN: automatic?



I was trying to figure out how to recover from bus-off, and found this
erratum for the PowerPC MPC 565.

Has anyone tested this to be true on a TouCAN module? On what chip? We
are using an MPC565 Rev D.

Thanks in advance.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
CDR_AR_1045 Customer Information TOUCAN.CDR3IMB3_05_1

CAN: Bus Off recovery not ISO compliant

DESCRIPTION:
The Bus Off recovery is not ISO compliant on the FlexCAN and TouCAN
modules. The
ISO specification indicates that the CAN node should remain inactive
until user
intervention restarts it. The FlexCAN and TouCAN modules both include an
automatic
recovery mechanism for the Bus Off condition.

WORKAROUND:
The Bus Off condition interrupt should be enabled and an interrupt
service routine
implemented to disable the CAN. The user's software should then
determine when the
CAN should be re-activated.

Rick Corey - Crane Aerospace
Lynnwood - 425-743-8469
Mobile - 908-887-0722

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