BUSLIGHT, BUSHEAVY & BUSOFF

[G.Lang]

At a CAN-bus there are several possible types of errors:

-> bit-errors
-> Form errors
-> Stuff errors
-> CRC errors
-> Acknowledge errors

For detailled infos about this errors please take a look at http://www.wikipedia.com (keyword: CAN-bus)

All these errors will be counted by the error-counters (a receive error counter and a transmit error counter) from the CAN-controller. There´s no time intervall for the count. For each transmitted or received message the error counters will be increased respectively decreased.

After a reset both counters are 0. In a range between 0 to 127 the CAN-controller are "error activ". This means that a CAN-node which detect as first node a receive error sends a flag (error active flag) to the CAN-bus. Through this flag the message will be unvalid for all CAN-nodes and the error receive counter of each receiver will be increased by 1. The node which detect as first node the error increase his counter with 8 points. After a succesfull transmission of a CAN-message the transmit error counter from the sender decrease by 1. After a succesfull reception of a CAN-message the receive error counter decrease also by 1.

At 128 error points the CAN-controller works in a "error passive" mode. The CAN-node is fully functional working in this state, but if the node detect an error he signalize this with a passive error flag. This flag don´t destroy the CAN-message and the CAN-node must wait some time before he can send a CAN-message. This prevented that a CAN-node with a high error-rate blocked the bus.

The "bus-off" state is reached when the error counter is higher than 255 error points. In this state the CAN-controller is disconnected from the bus.

Note: If an "error passive" CAN-node detect an acknowledge error he don´t increase his transmit error counter furthermore. This avoid that a transmitting CAN-node without any (other) acknowledging CAN-node in the system go into the "bus-off" state.

Buslight: appears by more than 96 error points, the CAN-node work in the "error active" state

Busheavy: appears by more than 127 error points, the CAN-node work in the "error passive" state

Busoff: appears by more than 255 error points, the CAN-node is disconnected from the bus

[sanoj]

Is there any possibility to "reset" the bus when bus heavy occurs (I'm using the Basic API from C#)? Or how should a CAN client application be able to properly come again and communicate with nodes on the bus?

cheers,
Jonas

[U.Wilhelm]

Yes, call CAN_Uninitialize(..) to close the session and then CAN_Initialize(..) to Reset the CAN Cotroller again.

[Jacquier_Kuhn]

Hi,
Is it possible to know how long does it take to reset the CAN controller?
My side, I use a PCAN-USB (not pro or hub) version with or without (we have both) galvanic isolation.
But because it is a global subject, perhaps could you response for all controller types.

Best regards,

Pierre

[U.Wilhelm]

On the PCAN-USB a Reset need round about 700ms (complete Reset). There is no differnet between isolated or non isolated version.