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Altera_Forum's avatar
Altera_Forum
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15 years ago

signal II tap issue with I/O BUS

Hello and thanks for any help.

I am using signal II tap to debug an I/O Bus between FPGA and DSP. My design works fine in timing simulation and I do see my "BUS~result" showing count up to the DSP synchronized to a common clock between the two devices.

However in signal II tap my bus is always showing <0000>, the weird thing is that if I tap into the count signal that feeds the BUS signal I do see the count up working but not on the actual BUS signal.

Any remarks are greatly appreciated.

thx,

Mowa...

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    Are you sure the count signal is feeding the output pins? are these pins bidirectiona? if so are you actually driving them?

  • Altera_Forum's avatar
    Altera_Forum
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    Thanks for the reply,

    I am pretty sure I am driving them and the timing simulation confirms, the bus is bidirectional. I wonder if there is something funny about the PINS in S2T?
  • Altera_Forum's avatar
    Altera_Forum
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    May be you better start with a fresh signaltap.

    I asked about bidirectional pins because a pitfall may occur if you are not driving it correctly at the right time. It could be the DSP chip is driving it with zeros.
  • Altera_Forum's avatar
    Altera_Forum
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    thanks,

    I will give it a shot. Are you aware of any special case where S2T can't access a Bidirectional Bus because some XYZ reason?