CP3BT23_14 Datasheet, PDF (144/324 Pages) Texas Instruments – CP3BT23 Reprogrammable Connectivity Processor with Bluetooth and Dual CAN Interfaces

CP3BT23
SNOSCX3A – JULY 2013 – REVISED JANUARY 2014
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18.6.3 Transmit Procedure
The transmission of a CAN message must be executed as follows (see also Figure 18-24)
1. Configure the CNSTAT status field as TX_NOT_ACTIVE. If the status is TX_BUSY, a previous
transmit request is still pending and software has no access to the data contents of the buffer. In that
case, software may choose to wait until the buffer becomes available again as shown. Other options
are to exit from the update routine until the buffer has been transmitted with an interrupt generated, or
the transmission is aborted by an error.
2. Load buffer identifier and data registers. (For remote frames the RTR bit of the identifier needs to be
set and loading data bytes can be omitted.)
3. Configure the CNSTAT status field to the desired value:
— TX_ONCE to trigger the transmission process of a single frame.
— TX_ONCE_RTR to trigger the transmission of a single data frame and then wait for a received
remote frame to trigger consecutive data frames.
— TX_RTR waits for a remote frame to trigger the transmission of a data frame.
Writing TX_ONCE or TX_ONCE_RTR in the CNSTAT status field will set the internal transmit request for
the CAN module.
If a buffer is configured as TX_RTR and a remote frame is received, the data contents of the addressed
buffer will be transmitted automatically without further CPU activity.
Write_buffer
Write
TX_NOT_ACTIVE
Yes
TX_BUSYx?
No
Write ID/data
Write
TX_ONCE
or
TX_ONCE_RTR
or
TX_RTR
Exit
DS041
Figure 18-24. Buffer Write Routine
144 CAN Module
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