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Old 07-08-2003, 01:44 AM
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Default Re: [DLL usage Virtex/Spartan-II] HowTo drive CLKDV Div 2 off Chip

Be carefull. Usually when you instantiate a ibufg, you are actually
instantiating a IOB configured as an input, and a bufg. You only want to use an
IOB as the input and make sure it is loc'd to a clk input pin location.

As for your div/2, you can divide the input to the dll by 2 using the
CLKIN_DIVIDE_BY_2 parameter. Don't know if this helps because the clk0 will be
div/2 since the dll is dividing the input to the dll.

Markus Meng wrote:
> Hi All,
> some notes I could not figure out directly from one of the XAPP132, 174
> from Xilinx. If I want to drive an Off-Chip device with half of the clkin
> frequency
> without using a GBUF driver, can I feedback the devided signal from the obuf
> driving the pin through an IBUFG and still having the DLL functionality of
> phase
> shift an duty cycle correction. I read that the feedback signam MUST be
> clkout
> or 2xclkout. The problem is that I am running out of GBUF's in my design ...
> markus

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