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[Moved]: TDC IC start and stop

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vinogunasekaran

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Hi, I wanted to measure the frequency of a signal using a TDC. Typical TDC's uses a start and stop signal as input. What does that mean and how does that help me in measuring the frequency of my signal
 

Re: TDC IC start and stop

Hi,

Where is the problem?
Don´t want to read the datasheet? --> There is no way round this.

We can´t read the datasheet, because we don´t know the partname. And we don´t need to read it, because it´s your job.

*****

imagine it works likes a stop watch:
Start, Stop, --> Then it gives the time between start and stop.

Frequency calculation should be no problem.

Klaus
 

Re: TDC IC start and stop

Yes i understand that it gives the time period between start and stop. But I have only one digital signal as input , whose frequency is to be counted. What will my stop input be? (eg. TDC7200)
 

Re: TDC IC start and stop

I've never used a TDC7200 but from the data sheet I can see it has no automatic method of sensing any point in the incoming signal, you have to provide them (start and stop) yourself.

If using it only as a frequency counter, you have to provide it with a known 'gate' or 'capture window' signal from a reference source. For example if you provided a signal that went high for exactly one second then went low again and applied the rising edge to start and the falling edge to stop, the measurment would be in cycles per second (Hz). By usung longer or shorted gate periods you can adjust the range of frequencies it can measure.

Brian.
 
Hi,

Reading datasheet is always a good idea:

In one of the first sentences on the first page it says:
The ability to measure
from START to multiple STOPs gives users the
flexibility to select which STOP pulse yields the best
echo performance.

Use an async signal START
and your testsignal as STOP
... then measure between two STOPs.

Klaus
 

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