Suppose all nodes in a CAN network are configured using acceptance filters to rx packets that are addressed only to them. Example: Node A configured to rx packets addressed only to "A" in the 11-bit ID field and so on.

Scenario: If there are four nodes, A, B, C, and D.

Question 1: If A addresses a packet to E (not a valid ID), will node A's ACK flag be set indicating that a message has been acknowledged by a node? That is, if a message is not accepted by an acceptance filter, will, whether a message has been rxd or not be known to the sender.

Question 2 (depends on question 1): If A addresses a packet to D (valid ID), does acknowledgement of the message indicate that only D has successfully received the message? Or, does it mean that all nodes received the message though their acceptance filters are configured to rx only their specific IDs?


1 Answer 1


ACK only means that the raw message was received intact. There were no timing violations that would cause a message to not be detected, and the checksum matched. Filters work at a higher level.

  • \$\begingroup\$ Thanks. So there's no way of knowing if a node fails in a multi node network cos even if 2 nodes are functional,the message will be acknowledged \$\endgroup\$
    – AlphaGoku
    Jan 23, 2016 at 17:06
  • \$\begingroup\$ @Aks: Yes, assuming the other nodes don't fail in such a way to make the whole bus inoperable. \$\endgroup\$ Jan 23, 2016 at 17:08

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