Spartan FPGA boards - two questions

Archive SparkFun Site Questions/Comments
1

I’m playing with Spartan FPAs, and would like to try the 3E boards from Sparkfun. I have wo questions:

  1. Is the FPGA on the breakout-board the same as the breakout & development board? The latter has a 500k 3E chip, but the code associated with the breakout-board only is or a 250k device. I would like to use the dev board to design stuff, and use the lower-cost breakout-only for final use.

  2. Has anyone used a programming device other than the parallel port cable to program these boards? With parallel ports disappearing,having an alternative would be good. I’m thinking specifically of the Digilent USB cables, such as he JTAG-USB full-speed cable, at $39.95. Before I buy one, I’d like to make sure it works.

I’m presently using the Digilent Nexys2 boards for learning and designing, but they do not bring out enough FPGA pins for my project.

I’m also thinking of using a Sparkfun Wiznet board as an enet interface to the FPGA instead of USB. Woud this work?

Thank you

Terry

WB4JFI

2

  1. According to the schematics, they are both 500K gate parts. When you resynthesize the demo code, it will work fine on any FPGA. Just make sure you locate the signals properly.

  2. I still use a Digilent parallel port JTAG programmer but I know many people who use USB versions. Digilent sells them so you know they work. I’m not positive if they integrate with ISE like the parallel version does. You may have to run separate programming software.

The FPGA can run with nearly any other IC connected to it so the Wiznet will work just fine as would USB, even at the same time. You could even hook up a gigabit ethernet PHY and run that too.

-Bill

3

Thank you for the reply phalanx. I have the breakout plus development board already, and was successful in getting the counter program to work, after some minor channges (changed to 500k FPGA, and changed ucf file).

So, I can now download through a homebrew parallel cable made like the Sparkfun one(a Sparkfun parallel cable has been ordered and is on the way), and see the outputs change with the counter.

However, I cannot seem to program the onboard 45DB161D SPI PROM. I’m using Impact 11.1, and as mentioned, can program the FPGA itself fine. I’ve followed the instructions in the Spartan 3 Config User Guide, chapter 2, as close as possible (version 11 has a little different prompting). I’ve created a .mcs file, and tried to upload it (using both the auto-size and an 16Mb part size). The SPI Prom does show up above the FPGA in the little graphic window.

Whenever I try to do a blank-check, erase, or readback, the results are intermittent. The programming always stops at about 11 seconds, I think where it starts verifying and failing. There are occassionally some messages about the device never setting the ready line.

The device ID seems to come back as all zeroes most of the ime, instead of what it’s supposed to. Since the FPGA programs correctly, and the FPGA programs the Prom through it’s SPI, could the Prom be bad? Or, could my homebrew parallel programmer be bad for SPI programming, but OK for FPGA programming (unlikely)? I am using 74HC125’s instead of 74ACT125s, but the HC’s are used on the Xilinx cable, and I already had them.

Lasty, When you are programming the SPI PROM, the instructions say to set the M0-M2 jumpers for SPI Master. I’ve tried that, and I’ve tried the jumpers set to JTAG. Which should it be? I thought the Mode jumpers were for reading the FPGA config setup at power-up or reset, and don’t really affect the writing to the SPI Prom. But, as mentioned, I’ve tried it both ways.

Any help is apprecated. Let me know if I need to provide more info.

Terry

4

I hate to answer my own post, but it’s now WORKING (!) and here is what I found.

I tried several things, like shortening the parallel port cable, etc. No go. Then, I shortened the JTAG cable between the program/buffer board and the FPGA board. It was about 12-inches, I shortened it to about 5-inches. Viola! I guess the HC125s don’t have the drive to push that much cable.

I declare success, and am now considering how to do this with a USB cable (like Dave, posting elsewhere). I hope the Digilent cable allows indirect SPI PROM programming, as I’m getting tired of moving the one computer all over that still has a parallel port.

Terry

5

Seems like you might be a little ahead of me. I found app note XAPP974 - Indirect Programming of SPI Serial Flash

PROMs with Spartan-3A FPGAs, which filled in a lot of gaps for me.

6

wb4jfi:
I hate to answer my own post, but it’s now WORKING (!) and here is what I found.

I thought those were the best kind of posts--you get an answer and everyone else does too. :)

–Philip;

7

I’m glad you figured it out!

I’ve never ran into this problem because I tend to use the Xilinx configuration PROMS which appear in the JTAG boundary scan and can be directly written to using iMPACT.

I’ll have to play around with using a generic SPI EEPROM.

-Bill