Well, I'm not sure if anyone here has had the same problem, but I have, and it has been driving me nuts. My primary machine is a laptop, which has no parallel port, so I am stuck with USB. Also, I am in a class where we are doing projects using the Spartan-3 Starter Kit from Digilent.
Since I have no parallel port, I have been using Digilent's JTAG-USB cable, which, for the most part, works great. However, there are two problems.
- You cannot use Xilinx IMPACT to program the Spartan-3
- The external SRAM does not work when using a .bit file
Well, #2 seems awfully strange. I know it did for me, I thought I was having a problem with VHDL, and that's why I thought it wasn't working. Well, I spent a long time tinkering with it over our winter break (I know, I know, but it's what I did) and just today I came up with the solution.
A little explanation for this is probably needed. Basically, anything I write and compile in IMPACT would work fine. LEDs light up, the
7-segment display works fine, everything I've done works great. However, every time I tried to write to the SRAM, nothing changed, I simply got back garbage/random data. Every time, no questions asked, it just didn't work. To make a long story short, here's a solution I discovered (which, is a whole another story to how I figured it out).
- Start IMPACT
- Edit -> Add Device -> Xilinx Device
- Loaded c:\Program Files\Xilinx\spartan3\data\xc3s200_ft256.bsd
- Right-Clicked Device, Assigned Configuration File
- Mode -> File Mode
- Clicked SVF-STAPL-XSVF tab, clicked "Yes" when it asked to load from Boundary Scan
- Chose to generate a new SVF file, named it
- Right-Clicked Device, chose Program.
- Output -> SVF -> Stop Writing to SVF File
- Quit Impact
- Started Export, did Device Scan, loaded SVF into the xc3s200, set the prom to bypass, hit program. Everything worked right.
Seems like a strange solution, but what I want to know, has anyone here had a problem like this? I have a feeling that loading a different .BSD file for other Xilinx chips should work just as well with the JTAG-USB cable/Digilent's ExPort software, but I couldn't tell you.
Hope this helps people out.
If anyone wants to contact me with any more information via email, please use: skroll at gmail dot com