TMS320F28069: TMS320F28069 CAN issues

I realize you are using the term “closed” to indicate a bus-off condition.

1. Is the CAN bus sending closed after the transmit error counter has accumulated to 255?

Yes. Once a node is in bus-off, the node cannot transmit anymore.

2. After can bus closed, whether it will effect receiving data or not?

Whether or not it keeps receiving frames depends on the implementation in the design.

3. When will the bus automatically return to normal? Is the transmit error counter cleared directly from 255 to 0? Or slowly decrease to 0 ?

In order to come out of bus-off, a Bus Off recovery sequence has to be executed. Such recovery can either be automatic or manual.

Automatic: A CAN bus node (ECU) automatically goes bus on after 128 x 11 (recessive) bits, which is the equivalent for 128 messages. The 11 bits is the recessive time between messages so even in a 100% loaded bus, a bus off node will go bus on again.

Manual: This involves user application writing to certain bits, after which the node will wait for 128 * 11 recessive bit times before it commences communication.

TEC is cleared directly from 255 to 0.

4. The data cannot be sent after bus sending is turned off. It is not possible to judge whether the transmission is successful, and the counter value of transmit error counter cannot be reduced. Always 255?

Sorry I don’t understand the question. TEC cannot be reduced manually. Once the node enters bus-off, TEC is cleared and the recovery can be wither automatic or manual as described above.