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How to get two different frequency signal synchrously?

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toxichucky

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hello everybody,
I have two different frequency signal.
One is 100Hz, the other is 5kHz.
I have to get the two signal synchrously to do something.
Can anybody tell me how to do it?
I have tried to use DFF, but it needs plenty of DFF.
Best Regards.
 

echo47

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Please clarify the source of these two signals, and what you are trying to do with them.
 

toxichucky

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I would like to capture two signal from RS232.
one of the sampling rate is 5KHz,the other is 100Hz.
I need to add the two data bit to bit.
cause the different sampling rate, the added result will be incorrect.
I tred to use delay element like D-filp flop, but it need lots of DFF.
I would like to know how can I get the two signal synchrously.
Best Regards.
 

kavitha_bonthu

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if you can afford latency in your design why cant you try with memory which write at one frequency reads at other frequency.
in your case take two memories one for 5MHz,and one for 100Hz.
for 5Mhz memory both writing and readin will be at the same rate.
where as for 100Hz memory writin at 100Hz reading at 5Mhz.
since both memories reading at same frequency proceeding in your design will be easy.
 

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toxichucky said:
hello everybody,
I have two different frequency signal.
One is 100Hz, the other is 5kHz.
I have to get the two signal synchrously to do something.

Why don't you synthesise the second clock from the first so you'll get 2 synchronous signals. This is possible by dividing 100 Khz by 20 to have the low speed clock.

Another beter solution is to use a PLL.
 

robinh

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Yeah, I think the best solution is to use a DLL or PLL macro with proper settings in order to make one frequency from the other.

Have a look at the datasheet of your FPGA. There are also many examples with all FPGA manufcturers (Application Notes).
 

alzomor

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Hi

If you are using Virtex FPGA you can make use of DCM or PMCD

Salam
Hossam Alzomor
www(.)i-g(.)org
 

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