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SN65HVD251: SN65HVD251 transceiver locks up bus

Matthew Plante
Prodigy 70 points

Part Number: SN65HVD251

Hello,

I have replaced an MCP2551 transceiver on an existing board with a SN65HVD251.  When the board is powered off, and attached to a CAN host, I can see traffic on the CAN bus as expected. 

image.png

If I power up the board, and leave the attached microprocessor in reset, I can still see traffic on the CAN bus. 

image.png

However, when the uC is taken out of reset (or allowed to come up on its own at power up), the bus becomes quiet and nothing will communicate. 

image.png

The boards works as expected if I replace the SN65HVD251 with an MCP2551.  I don't understand what the issue could possibly be.

  • +1
    Prodigy 70 points

    I solved the issue.  The problem was the microcontroller software set the CAN TX pin low after boot.  The micro never sent data because of the dominate state of the bus.  The old microchip CAN MCP2551 IC has a dominate "stuck ground" feature where it will release the bus if it sees the TX pin low for a certain amount of time, which is why it worked with the MCP2551 IC and not the TI part, which doesn't have that feature.