Differences
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can_bus_off [2013/03/21 11:06] – created heinz | can_bus_off [Unknown date] (current) – removed - external edit (Unknown date) 127.0.0.1 | ||
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- | ==== CAN Bus-Off condition/ state ==== | ||
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- | BusOff is an error state of the CAN Controller. Only the transmitter can switch in the state BusOff, if the //Transmit Error Counter// exceeds 255. | ||
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- | (more details needed on this place) | ||
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- | In real life a CAN controller can switch in the mode ErrorPassive sporadic. But the mode BusOff is a critical error and should never arrive without a hardware error or an other critical error. | ||
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- | ---- | ||
- | '' | ||
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- | there are 2 different ways to recover from bus off : | ||
- | * automatically after 128 occurrence of 11 consecutive ' | ||
- | * A node can start the recovery from »bus off« state only upon a user request. | ||
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- | That's right that we can find on the market these 2 ways according the used CAN core. This difference must be taken in account to have the same behavior in drivers and network management according the choosen CAN controller | ||
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- | '' | ||
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- | There is actually no difference. | ||
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- | If that were not the case then a node with a defective receiver would try to send, go bus off, then go bus on again and try to send thereby | ||
- | using 100% of the bus. The 128 * 11 makes it possible for 128 other messages to sneak through while this defective node goes through its bus | ||
- | on/off cycle. | ||
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- | The interesting thing about handling bus off situations is that on a wired CAN bus, unless there has been a major bus disturbance, | ||
- | off situation almost never happens. | ||
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- | '' | ||
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- | The ISO states that auto-bus on is not required, i.e. devices with auto-bus on feature are not 11898 compliant. We had this discussion with the Motorola TouCAN (which is still not conformance tested) and other CAN-contoller-cores. I heard also from several sources from CAN-industry that auto-bus-on is not wished very often. It makes more sense to let the application decide what should happen. Especially in the automotive-sector the auto-bus-on-feature is very negative. | ||
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- | '' | ||
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- | I would support Anastasios. We always suggest our customers, in the case our driver reports the BusOff situation to the application, | ||