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How to extend BDM Multilink
JOHN F. Jul 15, 2015 at 11:39 AM (11:39 hours)
Staff: Takao Y.

  • We bring the BDM pins from the MC9S08DZ60 processor to an external connector on our product so it can be field reprogrammed. Because our module is potted, we do not have access to the 6 pin BDM header directly.  We made an adapter board convert the 6 pin ribbon cable to our external connector.  For access in the field, the cable we use is about 18" long.  We are experiencing stability issues when reprogramming this way.  Sometimes it won't connect or loses connection during a reprogram.  Is there a way to reliably extend the connection?  I have tried twisting the ground wire with the BKDB wire but it made no difference.


  • Greetings,

    Our recommendation is using the 6-pin ribbon cable that comes with our hardware products. Our ribbon cables are 6 inches (0.15 meters). Anyone who adds length to the ribbon cable or includes any adapters will introduce instability.

    First, I would suggest trying your adapter with much shorter ribbon cable to ensure the problem is in fact the ribbon cable length. If the problem persists even with short cables, then the problem might actually be the adapter.

    If the problem is cable length then:
    1) Reduce the length closer to 6 inches
    2) Shield the ribbon cable. This can be done by purchasing a roll of shielding foil that can be found on or possibly your hardware store.
    3) Repurpose a long Ethernet or USB cable you may already have. Those cables already have shielding and made to work long distances.

    Takao Yamada

  • Option 3 would seem to be the most practical.  Can you recommend which wires to pair together in the ethernet cable?  For example: BGND, VCC, GND, RESET

  • Greetings,

    That is something you need to figure out yourself. It should not matter what wire you use. It is all one-to-one from one end to the other. There is no conversion going on in the wire. Just cut both ends off of the Ethernet cable and solder 4 pins to 4 wires.

    Takao Yamada

    • ok. Usually wires are twisted paired because they are differential signals and it makes a difference.  These are not differential signals that's why I asked.

  • Greetings,

    Any update on this? Did my suggestion to use an Ethernet cable work?

    Takao Yamada

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