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Altera_Forum's avatar
Altera_Forum
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12 years ago

JTAG to send a syncronized pulse to a large chained set of dev kits?

Hi,

I have a set of these ARRIA V starter cards http://www.altera.co.uk/products/devkits/altera/kit-arria-v-starter.html

Without going into much detail regarding why this design choice,

I'd like to know if it is possible to use the JTAG header on the kit? (or JTAG via PCI Express. preferably.)

to send a synchronous trigger pulse to all the cards to run a module.

If yes, a few pointers regarding how would be very helpful. I understand one of the cards will have to act as the master.

Or the PC Motherboard they are plugged into in case of PCI Express.

Thanks

ZubairLK

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    I'm sure you'll be able to use the JTAG header on the board itself, although, I seem to remember you need to change one (or more) switch settings on the board to get it to work. The on-board Blaster circuit has priority.

    As for JTAG to the PCIe connector, you'll have to check the schematics. Altera may not even take the JTAG chain to that connector - they not obliged to.

    You want to...

    --- Quote Start ---

    ... send a synchronous trigger pulse to all the cards ...

    --- Quote End ---

    I'm unsure how you expect to trigger all your cards synchronously via JTAG. It's a slow, serial protocol. If you daisy-chain a number of cards you'll end up clocking all your control stream through every JTAG device on each board. They'll be very little 'synchronous' behaviour between FPGAs on different boards once all the JTAG signalling is digested.
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    Does your PCI express motherboard support JTAG, do you have software drivers to operate it?

    In principle (by design of the JTAG protocol), it's possible to update data registers of multiple devices in a JTAG chain simultaneously. Practically, I doubt that it's supported by standard tools, e.g. Altera Quartus.

    With reasonable effort, connecting a hardware wire between the boards that propagate the trigger seems preferable. What's an acceptable delay and skew for the trigger?
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    --- Quote Start ---

    Does your PCI express motherboard support JTAG, do you have software drivers to operate it?

    --- Quote End ---

    Good question. Nothing stated in the Motherboard manual. And software drivers is a different story. Will require developing if its possible..

    This path seems to be too much of a bother.

    --- Quote Start ---

    In principle (by design of the JTAG protocol), it's possible to update data registers of multiple devices in a JTAG chain simultaneously. Practically, I doubt that it's supported by standard tools, e.g. Altera Quartus.

    --- Quote End ---

    I see. Thanks for the heads-up.

    --- Quote Start ---

    With reasonable effort, connecting a hardware wire between the boards that propagate the trigger seems preferable. What's an acceptable delay and skew for the trigger?

    --- Quote End ---

    Delay is no issue. Can be seconds even.

    Of the top of my head, skew between all fpgas when they trigger should be less than 5nS.

    Slightly off-topic.

    But would a broadcast packet via ethernet accomplish this? There are gigabit ethernet ports available on the dev kit..

    Edit.. PCI Express also has multicast. I can't seem to find skews for them though..

    Thanks

    ZubairLK

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