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Old 11-11-2003, 09:44 AM
Tolgay Akkaya
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Default Multiple clock domains in a FPGA (using DLL's)

I am targeting a Spartan IIE (400E) device with four global clock
buffers (BUFG) and four DLL's.

But I need five clock domains 25MHz(clkin, DLL1), 50MHz (clk2x, DLL1)
and 30MHz (clkdv, DLL2), 60MHz (clkin, DLL2), 120MHz (clk2x, DLL2) in my

I know that it is not allowed to use more than 2 BUFG per DLL.

I would like to use the DLL's to have a zero propagation delay and low
clock skew between output clock signals distributed throughout the
device. The primary global nets are driven by global buffers (25, 50, 60
and 120 MHz).

The 30 MHz clock domain (internal) is not so critical, so maybe I can
use a secondary global nets?

How can I drive the secondary global nets with an output of the DLL e.g.
the 30 MHz?

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DLL usage, multiple clock domains on FPGA. Tolgay Akkaya FPGA 0 11-11-2003 09:34 AM

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