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From: Scott M. Kroll on 7 Mar 2006 21:23
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.

1. You cannot use Xilinx IMPACT to program the Spartan-3
2. 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).

1. Start IMPACT
2. Edit -> Add Device -> Xilinx Device
3. Loaded c:\Program Files\Xilinx\spartan3\data\xc3s200_ft256.bsd
4. Right-Clicked Device, Assigned Configuration File
5. Mode -> File Mode
6. Clicked SVF-STAPL-XSVF tab, clicked "Yes" when it asked to load from
Boundary Scan
7. Chose to generate a new SVF file, named it
8. Right-Clicked Device, chose Program.
9. Output -> SVF -> Stop Writing to SVF File
10. Quit Impact
11. 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

From: Hendra on 7 Mar 2006 23:29
I don't know about your particular problem, but with regard to the
parallel port, you can buy a PCMCIA to Parallel port converter.
http://www.quatech.com/catalog/parallel_pcmcia.php
They should work for any FPGA board that needs parallel port since the
converter works at lower hardware level and it fools the operating
system to think that it really has a parallel port. From the device
manager, it would appear that you really have a native parallel port.
If you buy it , make sure you got rev. F or later. It fixed
incompatibility problem with some newer laptop. If you have the earlier
rev, contact them for the RMA and they will exchange it for you.

Hendra

From: Antti on 8 Mar 2006 02:30
#1 there is no way (til today) to create impact compatible 3rd party
programmers other than those that are cable III compliant, (unless usb
platform cable is integrated fully in the design) - hence the digilent
cable is not supported by impact

#2 this what I dont understand - FPGA and all connected stuff (SRAM
whatever) will work same way no matter what means are used to configure
the FPGA given the FPGA is really configured properly. So configuring
the FPGA with .bit file using impact or SVF file and some 3rd party
tool, should get the FGPA into same working condition.

If you had some trouble then its must some trick bug of the digilient
export software I guess

btw jtag config is a bit tricky, namly it is possible have DONE=1 when
FPGA is not configured at all etc..

Antti

From: Hendra on 8 Mar 2006 06:38
Antti wrote:
> btw jtag config is a bit tricky, namly it is possible have DONE=1 when
> FPGA is not configured at all etc..

One thing that I frequently see in some Xilinx FPGA boards is when you
got an error like Done is not high or something like that, you should
unplug the power cable, replug it and reprogram the board. If it still
doesn't work, unplug the parallel cable or whatever connection you have
as well.

Hendra

From: Brian Davis on 8 Mar 2006 07:31
Scott M. Kroll wrote:
>
> 2. The external SRAM does not work when using a .bit file
>
Could you clarify exactly what you mean here; are you
using the Digilent JTAG utility to program the on-board prom,
or to directly configure the FPGA via JTAG?

One thing I've seen with IMPACT generated SVF files on both
V2P's and the S3 starter kit, is the need for one last JTAG
operation to "wake up" the part.

IIRC, in the Digilent tool, after loading the FPGA with the
config PROM in BYPASS, just try a device id on the config
PROM and see if that fixes it.

Also, I think I've had to change the JP1 bitstream readback
jumper setting to "disable" to get consistent results for JTAG
download; you may also want to change the configuration mode
jumpers to "JTAG"

If the DCM doesn't start up after re-configuration, your static
logic would work but any DCM clocked logic would not:
Answer Record 11778:
"Virtex/-E/-II/-II Pro, Spartan-II/-IIE/-3 - Device configures
correctly after PROG is pulsed, but DLL/DCM/DCI does
not function correctly when reconfigured"

Similar things can happen if the part almost, but not quite, finishes
configuration and ends up in a configured state with GSR or GTS
still asserted.

To help sort out what is happening, create a test design with:
- an LED driven from a switch input (no registers)
- a blinky LED counter driven from the input clock WITHOUT a DCM
- a blinky LED counter driven from a DCM sourced clock
- LED's on DCM LOCKED and "clock stopped" status bit

Brian

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