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Contributor
Contributor
408 Views
Registered: ‎12-17-2019

High frequency generation

Hi,

i am using spartan 7 fpga,Board frequency is 100MHz but for my application(FIFO) needs 331MHz for writing ,I tried using PLL instantiation and i checked on oscilloscope 

i didn't get,can you guide me how to generate.

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7 Replies
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369 Views
Registered: ‎06-21-2017

A Spartan 6 PLL should be able to generate 331 MHz.  What do you see?  How are you routing the signal out of the FPGA?  Are you using a DDR register to output the clock as is recommended?  What is the Select IO type?  Are you going through a connector or are you looking on the board?  What is the bandwidth of you scope and scope probes? 

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Contributor
Contributor
284 Views
Registered: ‎12-17-2019

i am working on custom board so i routed the signal to connector,

clk_wiz_0
(
// Clock out ports
.clk_out1(wr_clk),
// Clock in ports
.clk_in1(clk)
);
wr_clk is my 331MHz clock .
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264 Views
Registered: ‎06-21-2017

You should use an ODDR register to drive a clock out of the FPGA.  Look in the Select IO Users guide (UG471) for a discussion.  What about the other questions?  What are the bandwidth of your scope and probes?  Are you probing on your board or at a connector?  Is the signal terminated in any way?

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Contributor
Contributor
253 Views
Registered: ‎12-17-2019

i am probing at a connector pin,and frequency's are getting change rapidly,
bandwidth of scope is 60MHz,thank you
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243 Views
Registered: ‎06-21-2017

What kind of connector  Is it a PMOD or an FMC connector?  PMODs are poor choices for high frequency signals.  Why do you expect to see a 330 MHz signal on a scope with only a 60MHz bandwidth?

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236 Views
Registered: ‎07-23-2019

As @bruce_karaffa indicates, you need:

1 - To have that output with a proper output buffer

2 - To have bring the signal to a high speed connector (FMC, SMA, etc)

2 - A proper oscilloscope with at least 1 Gsps, 500 MHz bandwidth

Another approach would be to take your 300 MHz signal inside the FPGA, divide it by something appropriate using some HDL) to have a few MHz and have that signal/ clock out to any pin (a PMOD would work with up to 5 MHz)

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Contributor
Contributor
188 Views
Registered: ‎12-17-2019

Thank you.
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