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How does a LIN bus slave device behave, if no master is connected?

In my research I noticed, that in LIN version 2.0 every message is initialized by a header frame which is sent by the master device. For tests I powered a LIN slave device and did not connect any master to the bus. Then I measured the voltage on the LIN bus line with an oscilloscope. And I seems that the slave device is transmitting data.

How can this be explained?

wewa
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3 Answers3

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Have you tried to decode the frames? Do they have the break period? sync byte? id? Possibly this is a master, not a slave.

user1139880
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That is not possible, i mean a slave cannot start the communication. The master has to send first a Header: - Sync Break Field (14 Tbit) - Sync Field (0x55) - ID field ...and when one slave in the bus detects that this request is for him, then replies, otherwise it ignores the received header.

amaia
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SLAVE can not transmit data if it does not get ID published by the master. Master must say first ID x please reply, then slave will reply. Otherwise your slave may be designed to keep on answering without request causing collision.

Sherif O.
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