• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 34 subscribers
  • Views 595 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

how to protect from accidental driving of multiple transceivers on a bus?

Mike Valvo
Intellectual 470 points
Other Parts Discussed in Thread: SN65LVDM176, DS91C176

hello,  In past and current projects using a half-duplex MLVDS bus, I've had situations where multiple transceivers were driving the bus.  Every time this happened, the transceivers would die.

1.  Is this expected? and why?

2.  what can be done (in hardware) to prevent this from happening?

3.  would the same thing happen on a full-duplex bus?

  • 0
    TI__Mastermind 43795 points

    Mike,

    I would not generally expect the MLVDS devices to cease functioning completely.  I would expect that clock-data activity would be disrupted during the output contention event, but once only a single driver was active on the bus the link would recover and resume normal operation. 

    How many drivers were "active" at one time?

    The MLVDS standard does not define a protocol for enabling just one MVLDS driver at a time.  This must be handled by the system, usually one entity would "master" the bus and control which device would be given permission to drive it.

    I'm not sure what you mean by full-duplex.

    One differential pair - with the capability to send and receive data at the same time

    Two seperate differential pairs - one transmitting in each direction.

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    Intellectual 470 points
    Lee,
    This has been observed with devices such as SN65LVDM176. if 2 devices are active (driving) at the same time, then both devices will be damaged. This has been seen in a multipoint configuration.

    what I meant for full-duplex was a multidrop configuration with 1 master and several slaves, where the drivers and receivers are separate. If more than 1 slave were to drive the bus accidentally, would the devices be damaged the same way the SN65LVDM176 devices do in a multipoint configuration? If so, how can I protect from that?
  • 0 in reply to Mike Valvo
    TI__Mastermind 43795 points
    I would try to substitute the DS91C176. It is pin compatible with the SN64LVDM176. It would be a good test to see if you still have troube with multiple devices driving the bus. I have connected several of these together in contention without seeing any problems after the contention is removed.
    Lee