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Altera_Forum's avatar
Altera_Forum
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8 years ago

LED to clock in Register

How to blink clock (CLK) in register?

Register code


module reg8 (CLK, D, Q);
input CLK;
input    D;
output   Q;
reg  Q;
always @(posedge CLK)
Q = D;
endmodule

Can i assign output LED = CLK?


output LED;
...
assign LED = CLK;

15 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    --- Quote Start ---

    Can you just give information how FPGA, 555 & LED's are interfaced?

    --- Quote End ---

    i don't know. i just connect 555 to FPGA "clock" input pin.

    for example, https://www.youtube.com/watch?v=jl43vj6ksmo

    --- Quote Start ---

    Let me know if this has helped resolve the issue you are facing or if you need any further assistance.

    --- Quote End ---

    OK, thanks
  • Altera_Forum's avatar
    Altera_Forum
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    --- Quote Start ---

    i don't know. i just connect 555 to FPGA "clock" input pin.

    for example, https://www.youtube.com/watch?v=jl43vj6ksmo

    OK, thanks

    --- Quote End ---

    An issue then is what is the high/low swing of your 555 circuit output (ie, what Vcc are you running the 555 device at? 5.0V). The clock input of most all modern FPGAs will be limited to (probably) 3.3V or 2.5V at most, so apply 5V to the clock input could cause damage to the FPGA device unless the voltage and/or current is limited appropriately.
  • Altera_Forum's avatar
    Altera_Forum
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    ok, let's go back a bit, what are you trying to do? could you explain what yoh are trying to achieve?

    Why do you want to use the external oscilator?
  • Altera_Forum's avatar
    Altera_Forum
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    Hm-m-m-m. Now i want to know what PLL is? What is it? How does it work?

  • Altera_Forum's avatar
    Altera_Forum
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    In verry simple terms it is a clock frequency modulator. It can take one clock and output another at a higher or lower frequency,