INIT_B stays low

Computer architecture


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INIT_B stays low

Postby salimbaba » Thu, 11 Nov 2010 04:29:55 GMT

I am using a daisy chain of 2 xc3s4000 FPGAs and an EEPROM xcf16p. The
chains goes like this : EEPROM -> FPGA1 -> FPGA2.

Now the problem is that i brought up the board like 4 months back, it
worked and then i put it back in closet. Today, when i needed it,i thought
it as fine but when plugged it, my INIT_B signal was constantly low where
as it should go high to 3.3V after few ms of POR.

I checked all the signals i could think of, checked for any short circuits
and stuff but couldn't find any clue. I checked my power rails and they
were stable, VCCINT 1.2, VCCIO 3.3 , VccAux 2.5 .

I have an external pull up to 3.3v through 4.7kohm on INIT_B signal.
It has just stopped working.

Can anyone give me some pointers?

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Re: INIT_B stays low

Postby John Adair » Thu, 11 Nov 2010 16:52:50 GMT

Check your configuration data has been generated for the correct
device. Also if you have increased configuration clock rate try
turning that down to normal.

You can gain a little more information using JTAG and doing a status
read of each FPGA device. Look particularly for a CRC error but also
check that your mode pins are set correctly in the status read data.

John Adair
Enterpoint Ltd. Home of Raggedstone2. The Spartan-6 PCIe Development

On Nov 9, 7:29m, "salimbaba"

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