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Altera_Forum's avatar
Altera_Forum
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17 years ago

I'm new to FPGA and have a question

Hi There,

I have recently purchased a DE1 kit with the Cyclone II FPGA on it.

I have had a go at VHDL and found it enjoyable, so far the most complex thing I have created was a 4 bit parallel adder.

What confuses me, and I am unable to aquire a clear answer, is how the FPGA holds its configuration?

I have a feeling it is being store in the 8 legged Flash/EEPROM that is next to it on the board and possibly that is loaded into a configuration RAM area inside the FPGA on startup, is this a correct assumption?

If so, is it possible to have the configuration data stored directly in the FPGA or would I be forever having to put a Flash/EEPROM chip with my FPGA on every design?

many thanks

10 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    You are correct on all accounts.

    If you use the Max II class of products from Altera, the configuration is stored inside the same part.

    Most FPGA's need to be configurated after startup, and usually from an external source.
  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    So this means I can design a board with a Cyclone II FPGA on it and have the configuration/firmware flashed directly into it?

    also, is the Cyclone II a flash once only device or can it be reflashed as you can with a Flash version PIC?
  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    No, you need an external configuration memory, usually a serial flash. Cyclone III also supports a parallel flash. The configuration memory can be programmed through the FPGA JTAG interface, so a minimal operational system consists of the FPGA, configuration memory, clock source, JTAG connector and power supply.

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    Oops, got a little too inclusive in the "on all accounts"

    Missed the sentence about "If so, is it possible to have the configuration data stored directly in the FPGA".

    My bad.
  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    ah good, all make more sense to me now.

    Would this mean I could program the configuration data to the serial flash using a common flash programmer (or homebrew) instead of having to buy the expensive JTAG equipment?
  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    Expensive? Terasic has a _better_ USB Blaster than Altera for $50.

    Plus, if I were to design my own board, I would design the USB Blaster (USBtoJTAG) into the board, itself. Terasic has done this with most, if not all, of their boards.

    Not having JTAG could be a _serious_ development liability.

    Cheers,

    - Ura
  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    If USB Blaster would be still too expensive, a homebrew ByteBlaster II (printer port operated JTAG adapter) could do. JTAG in-circuit programmability is usually the best solution for production scale, for development phase, JTAG interface is effectively indispensable, independant of main configuration source. In an embedded system, the FPGA configuration can be also provided by a processor, e. g. using passive serial scheme, but JTAG should be still designed to the board.

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    --- Quote Start ---

    Plus, if I were to design my own board, I would design the USB Blaster (USBtoJTAG) into the board, itself. Terasic has done this with most, if not all, of their boards.

    --- Quote End ---

    Yes, but there is a small problem, the USB Blaster specs are undisclosed. Some time ago I found somebody reverse engineered the USB Blaster though.