Probing Signals in FPGA

fpga probe freeware

Hi

Some times when i try to probe some internal signals, these signals dosn't function correctly.
Is it required to buffer any internal signal if I need to probe it on the FPGA IO's?

Salam
w ww.i-g.org

You do not need to buffer the internal signal. The IO block of the FPGA contains a built-in buffer. You cannot tap directly into the internal signal it is automatically buffered.

Why does the FPGA behave differently when you bring a signal out to probe? Usually this is a routing issue. If the external pin you are using as a probe point is on the other side of the IC, then the compiler will reoptimize the FPGA to try to minimize this added routing delay.

If you are bringing out multiple signals from the FPGA, then you should register all of them at the IO pin before you output them. Otherwise, the relative time delay of each signal will be different and you can easily misinterpret the signals. For example, if signal "A" is preceeding signal "B" on a scope. Is signal "A" really before signal "B" or does signal "B" have a very long routing delay within the FPGA?

There is another way to probe the internal signals in an FPGA... Vendors like Altera and Xilinx provide built-in signal analyzers like SignalTap and ChipScope. You can use these to probe the internal signals during runtime. These tools will output the results as a waveform which can be stored.

As far as the Xilinx ChipScope goes, this operates by using internal BlockRam as the storage function of the signal analyzer. To use this you have to purchase the ChipScope product and have sufficient available unused logic cells and BlockRams in your FPGA. Finally, you have to recompile with the ChipScope modules included.
While it can be a valuable tool, you have to have the resources available to use it.

there are a few block code analyzers that cost 0
and together with your mind and given ideas youll do a better job

look at the freeware core sims first esp linux ones....

youll find they offer free tools
and an api to build your own probes and tools
and a far better level of support via eboards

when you have success post your codes

and most often your learn far more thru the process
than some tool telling you it is as it is and you have no choices to confirm it

other than support and more questions

this way youll grasp far more info and build a better mind

....:|

internal signals are ttl and need no buffers

Dude,

I ve used the Signal Tap tool to tap some signals for Altera Devices. I have not used Chipscope but have heard it is very easy to use tool. May be u can try it.

I had a very good analysis with SignalTap.
Chipscope evaluation version is also available.

Thanks
Arun

Hi,
u can see the internal signals through software, which will be available in ur FPGA vendor itself.
for example xilinx - chipscope, Actel- logic analyzer

hi i am using Chipscope for tapping the internal signals... it is pretty easy to use...
the only disadvantage is the ammount of data you can capture is limited... because it uses internal block rams...