[SOLVED] CPLD, daisy chain JTAG

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  • [SOLVED] CPLD, daisy chain JTAG

    I have a circuit design in the works that uses an STM32 CPU and an ATF1508 CPLD. I have a J-link Plus. I have a couple of questions:
    Can I use the J-Link to program the CPLD? I don't see it on the list of devices. It is programmed by JTAG, and I have done so by coding the algorithm into a CPU on the same board and programming them in-circuit, but I'd like to simply wire this one to a J-Link socket on the board for simplicity.
    If it is possible to program the ATF1508, can I daisy chain them on the same JTAG connection? I have done this before: parallel connections for TCK and TMS, daisy-chain serial-linking of TDI, TDO-to-TDI, TDO-to-TDI, TDO back, etc.
    However, in this case, I have a +3.3V STM32 and a +5V ATF1508, and I'm not sure it will work.

    Anybody have any help for me?
    Jeff

    Jeff Casey
    Rockfield Research Inc.
    Las Vegas, NV
    casey@rockfieldresearch.com

  • Hi,

    You are on your own here. Daisy-chaining with 2 targets that use different I/O voltages is out of spec.

    Both targets either need to use the same I/O voltage to make things work, you you need level shifters at several points.
    For example the CPLD may create a 5V HIGH level on its TDO and put that onto the TDI of the 3.3V STM32… This is asking for trouble.

    You are probably better off by having 2 JTAG connectors on your PCB and do not any dais-chaining.

    For example by using the 10-pin leg-less needle connector, this should not take up much space:
    segger.com/products/debug-prob…rs/10-pin-needle-adapter/

    For programming the CPLD you may find JTAGLoad useful:
    wiki.segger.com/JTAGLoad
    Please read the forum rules before posting.

    Keep in mind, this is *not* a support forum.
    Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
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    Or you can contact us via e-mail.

  • Thank you. I apologize if I abused the forum, I did read the rules, and did search first, and realized I was off the standard track, thus thought it was an appropriate community quesiton.
    I have a test board out for fab -- it has jumpers to try a number of different configurations. If I do get anything unusual to work I will post it here. Cheers!

  • Hi,
    Do not worry, you did not abuse anything or break the rules.

    You are welcome to ask questions here.

    BR
    Fabian
    Please read the forum rules before posting.

    Keep in mind, this is *not* a support forum.
    Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
    Should you be entitled to support you can contact us via our support system: segger.com/ticket/
    Or you can contact us via e-mail.