BAT32G1x9 user manual | Chapter 22 CAN control
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Rev.1.02
22.13
Diagnostic functions and special operating modes
The CAN module provides receive-only mode, single-shot mode and self-test mode to support the
operation of the CAN bus diagnostic function or specific CAN communication methods.
22.13.1
Receive mode only
Receive-only mode is used to monitor incoming messages without any interference with the CAN bus
and can be used for the CAN bus analysis node.
For example, this mode can be used for automatic baud rate detection. The baud rate in the CAN
module will change until "valid receive" is detected, so the module matches the baud rate in it ("valid
receive" means that a packet frame is received in the CAN protocol layer without errors and there is a node
with the appropriate ACK connected to the CAN bus). Valid receive does not require message frames to be
stored in the receive message buffer (data frame) or the transmit message buffer (remote frame). Indicate
a valid receive event by setting the VALID bit of cnCTRL register (1).
Figure 22-57. CAN mode only receives terminal connections in receive mode
In receive-only mode, message frames cannot be transmitted from the CAN module to the CAN bus.
Packet caching is defined as sending a transition request for packet caching to be pending.
In receive-only mode, the CAN transmit pin (CTxD) in the CAN module is fixed to the recessive level.
Therefore, when a message frame is received, no active error flag can be sent from the CAN module to the
CAN bus even if a CAN bus error is detected. Since the transfer cannot be sent from the CAN module, the
transfer error counter TEC is never updated. Therefore, the CAN module in receive-only mode does not enter
the bus shutdown state.
In addition, after the packet frame is validly received, the ACK does not return to the CAN bus in this mode.
Internally, the local node recognizes that it has transmitted a reply (ACK). Unable to transfer overloaded frames
to the CAN bus.
LikeN macro
macro
Tx
Fixed to the
recessive
level
Rx
CTxD
CRxD