Data Acquisition Using XEM3005

Spartan-3 USB 2.0 Modules
1

Hi folks,
I have very basic question regarding capability of XEM3005. I plan to use it for data acquisition of my DUT. My DUT streams out data at a rate defined by a data clock that the DUT also sends out. The data clock pattern is a square pulse train with a very low pulse width (~20us) and pulse spacing (~40us), however, the data clock can be off for a unknown period of time (say ~1ms). So the data clock and the data do not have a constant rate. As I understand (and verified), I can use the BRAM on the FPGA to acquired these data without any trouble. If I want take more than 10MB data, I need to use the SDRAM. Is there a problem if I stream these data into the 32MiB SDRAM at the data rate defined by the data clock? You answer is much appreciated.
Many, many thanks.

Sincerely,
Yida

2

Hello Yida–

First, since your data “clock” is slow with respect to typical FPGA operating frequencies and can be discontinuous (off for 1ms at a time), you probably already know that you should use it as a “strobe” and not really as a clock input to the FPGA.

You can effectively stream data into the SDRAM, but there are some details.

You will want to put incoming samples into a FIFO, then burst them into the SDRAM when the FIFO has a certain number available. You can use our example SDRAM controller to do this, but will need to create the FIFO separately. The RAMTester sample includes a FIFO, for example. Rather than connecting the FIFO to the PipeIn, you could connect it to your incoming data.