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zubin_kumar31
Explorer
Explorer
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Registered: ‎08-23-2011

Reg: Oddball clock frequencies and module wise FPGA usage ...

Hi,

 

I had 2 questions regarding FPGAs ...

 

1) Odd frequencies - Using DCMs, its easy to generate frequencies like 100MHz, 25MHz etc. But how can I generate an odd clock frequncies like 11.6MHz, 13.2MHz etc.? What primitives might I need for this?

 

2) Module wise utilization - The design summary gives the overall usage. How can I find out how much FPGA resources each of my modules use up, without synthesizing them independently ...? Which report, design option might I need to access to get module-wise FPGA resource utilization for my design (in Xilinx ISE)?

 

Thanks and regards,

Zubin Kumar.

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austin
Scholar
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Registered: ‎02-27-2008

z,

 

1.  The DCM DFS synthesizes M/D, where M = 2 to 32, and D=2 to 32 times the input clock frequency.

 

If that isn't spot on the value you wish, you will need another crystal oscillator on the board.

 

2.  The reports after place and route in the verbose mode detail absolutely everything that gets used in the design.  How much is in each module is not important, as after synthesis, place, and route, you have no idea what got shared, trimmed, etc. so "module usage" is interesting, but the actual item everyone needs is "does it fit?"

 

You could place and route individual modules (with minimum interfacing so they don't get trimmed), but it will not match the final results (but it is somewhat useful).  The Xilinx IP data sheets do have estimates of the resources listed (example:  SEM IP core).

 

 

 

 

 

 

Austin Lesea
Principal Engineer
Xilinx San Jose
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bassman59
Historian
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Registered: ‎02-25-2008


@zubin_kumar31 wrote:

 

1) Odd frequencies - Using DCMs, its easy to generate frequencies like 100MHz, 25MHz etc. But how can I generate an odd clock frequncies like 11.6MHz, 13.2MHz etc.? What primitives might I need for this?


Either use an oscillator which runs at the necessary frequency, or use a device which has a fractional PLL which can generate the oddball frequencies.

----------------------------Yes, I do this for a living.
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