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Right now I have a DE2-70 kit in my hand.
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Ok, I have one of these kits.
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I have known about this and I've developed a build using the 8MB flash on the DE2 kit. I must use flash because I don't want to lose the data when the FPGA chip is power down.
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If you connect your DE2-70 to a PC via JTAG or Ethernet or serial, then you could always download to the board once it is powered on, eg., using System Console you can write from your PC into the SDRAM on the board. I just modified a design I created for the DE0-nano SDRAM and it works fine with the two SDRAMs on the DE2-70.
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It's just an example of what I want to do, which might be a little misleading. Anyway, I may have to set as many as 400+ pins.:cry:
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400 pins on what? An external device controlled by your DE2-70? Whether or not 400 pins is an issue depends on how fast you have to update them. If they pin states do not need to be updated rapidly, then a shift-register with double-buffered output registers is a simple solution (the double buffering allows you to shift a new value and then update all the values at once).
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Your suggestion of using a SPI flash seems feasible. But I don't know where is the serial interface of the FPGA chip and how to use the EPCS chip as a SPI flash. Would you mind pointing me out how to deal with this problem?
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There are Qsys components for accessing the flash. However, you've already figured out how to use the parallel flash, so I don't think the serial flash offers you any advantage.
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If I can load the data every time I start up the FPGA from the flash on the board, without having the JTAG circuit connected, that will be my best choice! Or maybe I have to use the JTAG and BIST commands.
One more thing, I said my data could be as large as 1MB. However, the size of the data depends the circuit I test. For most circuit, the data is no more than 200KB. So we can assume the maximum size of the data is 256KB.
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So what is wrong with using the parallel flash then?
The fact that you have not *clearly* explained what you are trying to do, indicates to me that we should still continue to discuss this. If you cannot clearly explain your objective to someone else, then you must not understand it yourself or perhaps are just having trouble explaining it, either way, if you can successfully explain to me what you need to do, and why these options are not suitable, then hopefully we can find a solution that is acceptable.
Cheers,
Dave
Honored Contributor
