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SN65HVD257 with redundant bus

Livio Franchin
Intellectual 835 points
Other Parts Discussed in Thread: SN65HVD257

Dear all,
In a safety application we are using SN65HVD257 CAN drivers in a Redundant Physical Layer CAN Network Topology as indicated in the relevant data sheet.
In case of two line cut failures on two different  buses (see figure attached), we encounter a problem as indicated here below.
Node A, the master of communication, is theoretically able to communicate with all the other nodes but, in practice, in the presence of the two failures above, the following situation occurs, which is intrinsic to the architecture:

·        When node A sends a data message to node B, this is correctly received by all nodes.

 ·      When node B sends a data message to node A, this is received by all nodes except node C which, however, receives the ACK bit sent by nodes A, B and D. In this case the CAN controller of node C interprets the ACK bit as a violation (frame error) and, therefore, destroys the message.

How is it possible to avoid this problem????
Regards
  • 0
    TI__Mastermind 20580 points

    Hi Livio,

     

    The design is extensible to triple redundancy (3 buses) if you really want to cover dual faults at the same time, just change it to a 3 input AND gate plus 3 XCVRs and buses.  The idea behind the fault signaling and detection from each node is that you would indicate a single bus failure and have it repaired before a 2nd failure could occur. With the fault signals and application s/w it is possible to control the network in various fashions.

     

    -- Scott