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Altera_Forum's avatar
Altera_Forum
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14 years ago

Can I mix C3 and MAX2 in a multi device JTAG chain?

Hi, I have found documentation concerning multiple device JTAG chain programming but have found non concerning if these devices had to be the same or differrent.

Cyclone 3 devices run on different power supply voltages than MAX II devices so I was wondering if I can mix them together in a single JTAG chain. I hope that the answer is yes.

I do realize that the Cyclone device needs a serial flash to maintain its configuration, so I plan to use the serial flash loader (SFL) to configure the serial flash after the JTAG devices are programmed.

Thank You

Tom

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    By design principle, JTAG supports different devices type and also different vendor's evices in a chain. This feature is baiscally well supported by Altera tools.

    If multiple IO voltages are involved, you have to check their compatibilty. At worst case, level translating drivers have to be used. Because the TDO/TDI chain is regenerated in each device, some additional signal delay can be tolerated. The most critical signal is TCK, because ringing edges can cause JTAG failure. This even happens with some single device JTAG designs. I suggest to provide an optional TCK buffer that can be populated if problems arise, otherwise bypassed by a jumper.