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Altera_Forum's avatar
Altera_Forum
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12 years ago

clock requirement, again

I had posted this question previous but received no satisfactory answer. I have a FPGA starter training board. I have been designing some sequential circuits using the TTL macrofunctions and conventional flip flops. The FPGA is a Cyclone EPC100... Sequential circuits require a clock and I do not know what pin to use as a clock. I would appreciate a simple solution, without being tossed around to books about PLL, etc. There must be way to get a clock and use it on the devices. I tried Pin 10, which is a clock output from the clock circuit of the board, but this did not work.

Any assistance will be greatly appreciated.

Best regards

Andrew

8 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    Your part number doesn't make any sense or is incomplete. It most closely resembles that configuration devices in its present form...even though you state it's a Cyclone device.

    I'm not sure what you're referring to as far as TTL macrofunctions. It may help to post a schematic or HDL sample of what you're trying to accomplish.

    If you can identify exactly which board and/or development kit you have then I could point you at example designs for it.

    As far as general FPGA design with Altera parts, take a look at some of the introductory training courses on the Altera website to get an idea of how things work as well as the following link/PDF: http://www.altera.com/literature/tt/tt_my_first_fpga.pdf

    Cheers and Good Luck!

    slacker
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    Check your board specs. Probably on the altera's site you would find the file with the pins positions. Download it and import it in your project. The read the board manual. It will tell you which pin is the clock, if it has one.

  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    The part number is Cyclone EP1C3T100C6. The Macrofunctions I am referring to can be found under MAX+PLUS II and they have the standard TTL numbers as 74XXX. The board is a low-priced Chinese origin board. My question is, I think, rather simple: What kind of clock do I connect to, say, a circuit such as a flip flop or counter that requires a positive or negative-edge clock to work. For a latch, I use Pin 41, is connected to a pushbutton switch and works as an enable pulse. However, a flip flop requires a clock.

    Thanks for any help you can provide.

    Veronis
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    I did read the proposed application note whose link you sent me, and it was very informative. I will try the PLL approach and I assume that the input to the PLL circuit is the general clock pin from the board, which in my board is Pin 10.

    Veronis
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    Slacker

    I read the app note you suggested. Here is what I am doing. I have all the pin numbers, and manual, etc. Chinese are not that great in their documentation. My board has a general clock circuit, which provides an output frequency of 50MHz that is connected to pin 10 of the Cyclone. I take this output and connect it to the PLL circuit. I connect the PLL output (c0) to the clock pin of the JK flip flop. I have connected the FF in toggle mode. I upload the circuit to the board and get a faint LED (not toggling). Maybe the PLL output frequency is too high for the FF.

    Veronis
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    If the LED is faint and not toggling then it's not being driven correctly. This could be for a number of reasons. Assuming you've successfully implemented what you describe then perhaps the most likely error is not assigning the output signal to the correct pin. This would, probably, result in the I/O being reserved with a weak pull-up - possibly enough to result in it appearing faint.

    So, check your I/O assignments via the Pin Assignments editor.

    If you still don't have any success, post some code for us to look at.

    Regards,

    Alex
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    Alex

    I have received several suggestions, none of which has helped me. I do not have code, the circuit is designed using the Schematic Editor. All I want and need is how and where (other than externally) get a low-frequency clock to driver, say, a jk flip flop or a counter or any sequential circuit. Novice stuff. My initial clock is 50MHz (coming from the board clock circuits) and I take it through the ALTPLL circuit but its does not seem to work. I need someone to tell me, in simple words (or even send a circuit) on how to get this circuit. So far, I am being referred to manuals that don''t help me. The board has a clock circuit (50MHz) that is connected to Pin 10 of the ECP1C3T100C6 Cyclone.I connect this pin (via the schematic editor) to the input of the ALTPLL. A simple question: If you wanted to show how a JK FF (with J-K connected high)toggles, what kind of clock would you use?

    Veronis
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    How fast do you want to toggle this flip-flop? What clock frequency are you trying to get out of the PLL?

    The ALTPLL has a minimum output frequency - 15.625MHz for Cyclone devices with a 50MHz input clock. You don't state what frequency you're trying to get out of it but I suspect, from what you say, you're hoping for something much, much lower.

    To generate a clock with a much lower frequency you will have to divide it down with logic.

    A screen shot of your schematic might help if you're still having problems...

    Cheers,

    Alex