TMS320F280039C: What's the meaning of message marker?

Kita Li

Intellectual 2295 points

Part Number: TMS320F280039C

Hi champs,

I found that in the 280039 MCAN demo "mcan_ex9_transmit" the message marker is set as 0xAA.

I have some question about that:

1. What's the meaning of message marker?

2. Why the message marker is set as 0xAA here?

Thanks

Kita

over 1 year ago

0 Joseph Casuga over 1 year ago

TI__Mastermind 38070 points

Hi Kita,

Currently looking at this. Will have a response by next business day.

Regards,

Joseph

0 Hareesh Janakiraman over 1 year ago

TI__Guru* 95315 points

Kita,

Sahil has explained this in this post: https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/1219036/tms320f280039c-q1-mcan---txbto-and-transmission-notification See below:

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.

0 Sahil Deshpande over 1 year ago in reply to Hareesh Janakiraman

TI__Expert 6035 points

Kita,

Kita Li said:
1. What's the meaning of message marker?

The purpose of the message marker is to link the Tx Buffer Element with the corresponding Tx Event FIFO element. Tx Event FIFO elements are used to store information related to the messages being transmitted and are generated automatically on transmission if the EFC bit is set in the Tx Buffer element. The order of transmission of messages can be dynamic (based on when the CAN bus is free, and in case multiple Tx buffers are ready for transmission priority is given to lower message identifiers) and can be tracked by the application through the Tx Event FIFO.

Kita Li said:
2. Why the message marker is set as 0xAA here?

It is an arbitrary value, the user can choose any value from 0-255.

Thanks.

0 Kita Li over 1 year ago in reply to Sahil Deshpande

TI__Intellectual 2295 points

Hi Sahil,

May I ask a more question about that? I am wondering why the maximal value of message marker is 255. I found that there are only 32 buffers in the chip.

How does the 7 bits of the message marker connect with MCAN's Tx Buffer Element/Tx Event FIFO? Could you briefly describe how the message marker should be configured?

Thanks!

Kita

0 Joseph Casuga over 1 year ago in reply to Kita Li

TI__Mastermind 38070 points

Hi Kita,

Message marker is an arbitrary value, meaning that this is a value that user will set. User has the option to choose any value from 0 to 255 and the value does not have to follow a serial order. For example, user can set the message marker for the first buffer as 'AA', then next buffer may be 'C0', then next may be 'D3' ... etc... Think of the message marker as a unique tag.

Regards,

Joseph

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TMS320F280039C: What's the meaning of message marker?