cyclone IV configuration: VCCIO8 connection

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My question is: VCCIO connects to pins A1, C4 and C7. Can I get away (at least for prototyping purposes) with soldering a wire on pin A1 (easy access on the PCB) and leave C4 and C7 floating?

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I would expect that all VCCIO8 bond wires connect to the same power rail, and the reason for multiple pins is current handing and inductance reduction. Given the same problem as you, I would just try it.

I mean hey, you can't make things worse right? As it stands, the device will not power on, ever.

Cheers,

Dave

Thanks Dave for your post.

Actually, following that philosophy (nothing to loose), the device did manage to boot a couple of times after connecting A1 and then the configuration failed (nSTATUS low again).

Given the measured impedance between A1, C4 and C7, those must be connected to the same rail, and given that no I/Os are connected to this bank in my design, I'm just wondering if the in-rush current at power-up is not too large to be handled by only one wire-bond.

Putting a 1000uF capacitance on that pin did not help (nor replacing the FPGA).

I know that not connecting VCCIO8 is probably not something anyone would do after reading carefully the datasheet, however I was just curious if anyone found his way around that issue...

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I'm just wondering if the in-rush current at power-up is not too large to be handled by only one wire-bond.

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For debugging purposes, you can defeat the "All power rails must come up within xxx ms, and must rise monotonically" requirement by holding nCONFIG low during power-on. Then let it go high, and it should attempt configuration from that point.

Cheers,

Dave

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Holding nConfig low during power up does not make it come high afterwards.

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nCONFIG is supposed to have a pull-up.

If you can hold it low using an on-board programmer, or just short it to ground, then power-up, then release nCONFIG, it should go high.

Cheers,

Dave

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I mean nstatus stays low after nConfig goes high...

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Look at the timing diagrams in this document:

http://www.ovro.caltech.edu/~dwh/carma_board/fpga_configuration.pdf

p4. nSTATUS should go high after nCONFIG comes high.

Probe around your board and make sure all the signals are in the correct state.

Do you have the JTAG connection wired up?

Cheers,

Dave

with the JTAG connected, the programmer software does not identify the FPGA device.

I'm not that familiar with FPGA hardware designs, specially with Cyclone IV, however I did design a couple of cyclone III based boards (schematic/placement/routing) without experiencing any of such configuration issues...

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with the JTAG connected, the programmer software does not identify the FPGA device.

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Does this device have a power-pad (pad on the bottom of the IC) and did you connect it to ground? Several people have forgotten to do this, and the device will not work correctly.

Cheers,

Dave