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the external reference clock mode of FMC230

[size=2]I have the combination of ML605 and FMC230 from 4DSP. I am wondering  what  the correct way is to configure FMC230 into external reference mode based on this combination?  [/size]
[size=2]I am trying to configure FMC230 , through ML605, into external reference mode with an extern reference of 30.72MHZ, but it doesn't work.  PLL is always not locked, and the FMC230 could not initialized correctly. [/size]
[size=2]There are some efforts I did.  [/size]
[size=2]First, I configured the FMC230 into internal clock mode with the bitfile of ML605,the initialization sequence in reference application provided by 4DSP and a few settings on PC console( 1 ML605 0 0). Then, that worked.[/size]
[size=2]After that, I moved to the next step and tried to configure FMC230 into external clock mode. [/size]
[size=2]What I did included (1) plug an external reference clock into FMC230 through RI port. The clock is from signal generator and the frequency is 30.72MHZ(the same as that of internal reference) with the input level of 0dBm. [/size]
[size=2]Then, I only switched the clock mode to the external reference mode(clock mode option is 2) on PC console[font=Verdana].[/font][font=Verdana] Except that,[/font][font=Verdana]  [/font][font=Verdana]I didn't modify anything, strictly following the previous initialization sequence. But the mode didn't work, even though the software toolkit was updated to the latest version.[/font][/size]
[size=2]By the way, I saw another topic was also regarding the FMC230 issue, but the reply was not clear.  Please  provide more detailed information if possible. [/size]

Hello Jerry,

External clock should work with the default reference design but you should place a clock as per the reference design expectations; You should connect a 2.5GHz (+10dbm) quality clock on he CI input.

The external reference is not used in external clock mode, the external clock settings in the reference application uses external clock but with internal (on board) reference clock.

Best Regards,

Hi Arnaud,

Thank you for the reply. After reading your message, I found a typo in my description,
"[size=4pt][font=Verdana]After that, I moved to the next step and tried to configure FMC230 into external clock mode. [/font][/size]"  , which might lead to sort of misunderstanding. Sorry about that. The mode I tried to configure was actually the external reference mode, instead of external clock mode.  If in this case, what should I do?


I'm sorry for the late reply. It sounds like you are doing correct. What you need to do is to give an 30.72MHz input to RI and run it with internal clock with external reference input mode. If the PLL does not lock, could you increase the input power?

Hi Kyu,

I did give an 30.72MHZ input to RI and run it with internal clock with external reference input mode, but PLL wasn't locked. I will increase the input power and let you know what's happening.


Hi Kyu,

With your suggestion,  I increased the input level to 10dbm and PLL was locked in external ref mode. Thank you very much.  But could you explain more about it, I'd like to know more details about it.

By the way, the input level shown in FMC230 user manual page 8 is 0dbm, is that incorrect,actually, right?




I looked up the datasheet of the clock device and it shows that 2V is reuiqred for input logic high. 0dBm should not be strong enough, however the User Manual also says LVTTL level supported. I will investigate this issue and update the user manual. Thank you for your feedback.

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