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CyclonII with empty EPCQ is driving to GND instead of being tri-state

Helmut
Beginner
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Hello,

 

since EPCS is discontinued I took an EPCQ32A for programming my EP2C15AF484C8N.

On  the board there are 2 EP2C15AF484C8N, each has an EPCQ-Eprom.

The FPGA is a hot-socked-fast-POR-FPGA-type. Since the power supply will  be too slow at power on, I keep the nconfig low (not my idea, it is recommended in the data sheet) with Schottky diodes until the supply voltage VCC_IO is in the range of 2.5 to 3.1V. The internal VCC_INT (1.2V) is derived from VCC_IO with an voltage regulator. This works fine since 10 years with EPCS-Eproms.

Now I have EPCQ32A Eproms, (I connect  a byte blaster to it - also can keep the plug open, does not matter) and switch on the power (to program the first EPROM).

There is a very high power consumption, the VCC_IO goes up to 3.1V only, since the regulator is at its limit. I see LEDs "on", which must be off at tri-state, so the FPGAs drive the LEDs and other (LVC) logic outputs to GND, shortening the logic outputs.

As soon as I start (only start, not finish) programming, the current is reduced, as if now the FPGA does not drive to GND. With both Eproms programmed the board behaves "normal". Now during configuration the FPGA is tri-state, the LEDs are off.

This only occurs with unprogrammed Eproms.

To my fortune there still remains enough voltage to program the Eproms and with 2 boards, it was fast enough, that nothing was damadged, but I think no damadge will not be guaranteed.

Do you have experienced a similar effect? What is to do?

 

Best Regards,

Helmut

 

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1 Solution
Helmut
Beginner
102 Views

Hello,

 

please ignore the entry above and delete it.

Reason: The EPROMs of the 2 FPGAs had not been empty, as supposed, they already were programmed with  some trash. 

So  the bad programming (of which I did not know) made the short circuit behaviour.

 

Pardon my error and this waste of time.

 

Best Regards,

Helmut

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1 Reply
Helmut
Beginner
103 Views

Hello,

 

please ignore the entry above and delete it.

Reason: The EPROMs of the 2 FPGAs had not been empty, as supposed, they already were programmed with  some trash. 

So  the bad programming (of which I did not know) made the short circuit behaviour.

 

Pardon my error and this waste of time.

 

Best Regards,

Helmut

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