Each Tx Buffer has its own Transmission Request Pending bit.
The bits are reset after a requested transmission has completed or
has been cancelled via register TXBCR.
TXBRP bits are set only for those Tx Buffers configured via TXBC.
After a TXBRP bit has been set, a Tx scan is started to check for the pending Tx
request with the highest priority (Tx Buffer with lowest Message ID).
A cancellation request resets the corresponding transmission request
pending bit of register TXBRP. In case a transmission has already been started
when a cancellation is requested, this is done at the end of the transmission,
regardless whether the transmission was successful or not. The cancellation
request bits are reset directly after the corresponding TXBRP bit has been
reset.
After a cancellation has been requested, a finished cancellation is
signaled via TXBCF
- after successful transmission
together with the corresponding TXBTO bit
- when the transmission has not
yet been started at the point of cancellation
- when the transmission has
been aborted due to lost arbitration
- when an error occurred during
frame transmission
In DAR mode all transmissions are automatically canceled if they are
not successful. The corresponding TXBCF bit is set for all unsuccessful
transmissions.
| Value | Description |
|---|
| 0 | No
transmission request pending. |
| 1 | Transmission request pending. |
