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Original question:

TMS320F280039C-Q1: MCAN Tx interrupt

TMS320F280039C-Q1: MCAN - TXBTO and transmission notification

Davide Dentoni
Prodigy 175 points

Part Number: TMS320F280039C-Q1
Other Parts Discussed in Thread: C2000WARE

Hello support,

in the case of transmission handled though dedicated tx Buffers, I need to manage this situation:

into the Tx interrupt ISR, I want to know which Tx Buffer has triggered the interrupt (i.e. which is the frame just sent).

My first idea was to use TXBTO, clearing it before leaving the Tx int ISR and reading it when entering Tx int ISR, but this register is not clearable by user sw.

If I read the register TXBTO under ISR, I find all bits to 1 because those bits are reset only by a new tx request (via TXBAR). Do you confirm ?

The only way I found is to create in sw a maks of bits, each one representing in real time the voluntee of sw to send a frame (sort of copy of TXBAR) and compare it

to TXBTO inside Tx INT ISR.

Do you have any suggestions about other MCAN registers that can be used to manage this use case ?

  • +1
    TI__Expert 6035 points

    Davide, 

    Davide Dentoni said:
    If I read the register TXBTO under ISR, I find all bits to 1 because those bits are reset only by a new tx request (via TXBAR). Do you confirm ?

    That is correct.

    Davide Dentoni said:
    Do you have any suggestions about other MCAN registers that can be used to manage this use case ?

    In order to track the transmissions, you can employ the TX Event FIFOs. 

    Step 1: Within the transmit frames that you want to track, set the EFC (Event FIFO Control) bit. This means that when the frame is successfully transmitted, relevant information for the frame is stored in the Message RAM in the form of TX Event FIFO elements.

    Step 2: In order to track which transmit frame corresponds to which TX Event FIFO element, you can use the MM(Message Marker) bits in the transmit frame. The corresponding TX Event FIFO element will have the same message marker.

    For more information, you can check out the relevant chapters in the TRM.

    There is an example on configuration of TX Event FIFO elements in the works, which will be available in the upcoming C2000ware release.

    In case of any further questions, please let us know.

    Thanks.