front panel indicator not updated in real time

[mar_just_one]

Hello,

I am using PXIe 7961R+6583.

I have single cycle timed loop clock by and external clock signal (strobe line). This loop contain a shift register which is actually a counter.

I want to observe this counter in the front panel in real time. Since my external clock is not contineous, tiying it directly to an indicator will not work.  I am using a register within the SCTL in which I write the shift register value. I am reading the register value in another while loop (running at top level clock rate) . The result is linked to an indicator. So in one sentence, I write to a register in a SCTL, then I read it parallely in another while loop and I connect the read data to an indicator.

Simulation shows a indicator with numbers running very fast ==> The is the expected behaivor. When running at target and when applying an external clock signal, the indicator is updated very slowly, there a lot of misses. The SCTL is executing correctly, however I can't see my indicator being updated in real time, it remains freezed most of the time. What is the issue?

I tried also with FIFOs...Same issue.

Regards,

Marwen. 

[mar_just_one]

Can anyone reply to me please?

Is is supported to execute single cycle timed loops using a strobe signal that is not contineous? (burst of 8bits for example) ?

Marwen.

[Miro_T]

Can you post your code? Which CLIP are you using? Can you describe your external signal( amplitude, frequency etc )?

I would start my investigation there

[mar_just_one]

I am using using the basic channel CLIP. My external clock swing from 0 to 3.3V at frequencies ranging from 1Mhz to 50Mhz.

My code is a simple timed loop that uses an external clock. When linking an indicator to the counter inside the timed loop, my code cannot even execute (after compiling). I get a message saying that a clock signal is not OK. Which is true since my clock is discontineous. When changing it to contineous everthing goes well. So I moved the indicator to a loop running at the top level clock rate and I transfered the counter value to this the indicator using a register (clock domain crossing)...Now I don't have error message before the execution, but I can't see my indicator being updated at a fast rate.

I will post my code later. 

Regaeds,

Marwen.

[Miro_T · Accepted solution]

Marwen,

From your description it looks like you have a Strobe line connected to your Single Cycled Timed Loop(SCTL). If this signal is not continues then I do see why you have this problem. This signal must stay continues and it must be running at the moment your FPGA code starts!

If you are looking to “sample” based on this signal then I would setup FAM clock as a source of SCTL and use your signal as a “trigger” to only record a sample on raising (or falling) edge of your signal.

Hope this helps