National CP3BT26 - Manual (Page 142)

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CP3BT26
19.12 USAGE HINT
Under certain conditions, the CAN module receives a frame
sent by itself, even though the loopback feature is disabled.
Two conditions must be true to cause this malfunction:
„ A transmit buffer and at least one receive buffer are con-
figured with the same identifier. Assume this identifier is
called ID_RX_TX. With regard to the receive buffer, this
means that the buffer identifier and the corresponding fil-
ter masks are set up in a way that the buffer is able to re-
ceive frames with the identifier ID_RX_TX.
„ The following sequence of events occurs:
1. A message with the identifier ID_RX_TX from an-
other CAN node is received into the receive buffer.
2. A message with the identifier ID_RX_TX is sent by
the CAN module immediately after the reception
took place.
When these conditions occur, the frame sent by the CAN
module will be copied into the next receive buffer available
for the identifier ID_RX_TX.
If a frame with an identifier different to ID_RX_TX is sent or
received in between events 1 and 2, the problem does not
occur.