TX Messages

Zynq UltraScale+ Device Technical Reference Manual (UG1085)

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2.4 English

The controller has a configurable TXFIFO that software can use buffer up to 64 TX CAN messages. The controller also has a high priority transmit buffer (TXHPB), with storage for one message. When a higher priority message needs to be sent, software writes the message to the high priority transmit buffer when it is available. The message in the TXHPB has higher priority over messages in the TXFIFO.

When arbitration loss or errors occur during the transmission of a message, the controller tries to retransmit the message. No subsequent message, even a newer, high-priority message is transmitted until the original message is transmitted without errors or arbitration loss.

The controller transmits the message starting with bit 31 of the IDR word. After the identifier word is transmitted, the TXFIFO_DLC word is transmitted. This is followed by the data bytes in this order: DB0, DB1, ... DB7. The MSB of a data byte is transmitted first.

The status bit, can.ISR[TXOK] is set = 1 after the controller successfully transmits a message from either the TXFIFO or TXHPB.

The messages in the TXFIFO and TXHPB are retained even if the CAN controller enters bus-off state or configuration mode.

The message format is described in Message Format.