Orange things with many pins on bus lines

Discussion in 'General Electronics Chat' started by jamus, Apr 30, 2014.

  1. jamus

    Thread Starter Member

    Feb 11, 2013
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    Can anyone explain to me what these orange things are and how they work? I often see them at the beginning and end of bus lines on various 1990s industrial electronics. Perhaps they are capacitors of some type?
    Here is a picture I found on the internet. Orange things terminating a bus.
     
  2. tshuck

    Well-Known Member

    Oct 18, 2012
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    675
    Looks like a SIL resistor array/network...
    [​IMG]
     
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  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Bus resistors, my guess too.

    Oft with an odd number of pins: a 9 pin device would have 8 resistors, each connects to the 9th pin.

    Used for a pull-up, down, or impeadance match useage,
     
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  4. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    What you have is a 4-slot VME J1 backplane. The small orange parts are ceramic and tantalum decoupling capacitors. The large orange parts are terminating impedance networks. For each address and data line and most control lines there are two resistors per line, 330 ohms to +5V and 470 ohms to GND. This sets up a Thevenin equivalent impedance of 194 ohms at 2.94V. Static current through the networks with no boards plugged in is around 1A.

    Most of the signals are bussed to the same pin at each slot. The groups of jumpers between slots control the bus grant and interrupt acknowlege daisy-chain signals. The jumpers complete a bypass around a slot; you install the jumpers if the slot has no board installed. Other backplanes use mechanical or electronic means to bypass empty slots automatically, and active bus termination.

    A full VME-64 compliant backplane is twice as tall and has another row of identical connectors, the J2 row, plus more terminators. There are not as many as for the J1 row because in J2 only the center column of pins has VME signals; the two outside rows are for user-defined I/O.

    ak
     
    Last edited: Apr 30, 2014
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  5. MrChips

    Moderator

    Oct 2, 2009
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    Resistor networks use for bus termination.

    [​IMG]
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    That photo is marked
    - 2 - 272
    which is a 2-pin resistor pack, with FOUR 2-pin independent resistors and 8 pins. 2k7.

    Doesn't bus termination use 8 resistors to ground?

    Tshuck's "9E" package is a 9pin bus 8-resistor pack type.
     
  7. MrChips

    Moderator

    Oct 2, 2009
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    Sorry, I just posted an orange looking resistor pack, not the exact one used on the VME card bus. AnalogKid has a better explanation above in post #4.
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Attached PDF, page 2, top right image.

    ak
     
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