I'd wonder why you'd want to bother with Verilog at all. If you're a 'C' programmer, you'll be sucked into one trap after another because of syntactic similarities. IMHO, you're better off with VHDL, which, BTW, is much more widely used throughout the world.


A little reading and a fifteen minutes with the software, and you'll be just fine.


The only thing you're likely to do wrong is to plug the cable in backward. The simulator is very good, and will show you what's wrong well in advance of any actual implementation.


A lot depends on what's on the board you're using. The board can make it very easy or very hard.



I'd spend a little time thinking about the assumption that blinking an LED is much less complicated (Is is somewhat more complicated, but not much.) than displaying a counter on a 7-segment display. It involves a counter, which is a registered device, a HEX=>7-segment encoder, which is a combinatorial device, and one additional tap. That additional tap, of course, could be your blinking LED, so you actually build it along the way.

What you've apparently overlooked is the tools that are at your disposal in, say, the XILINX Webpack, or the Altera Quartus-II Web edition, both of which are free downloadable tools. I don't know about Quartus, but the free XILINX tool allows you to choose either Verilog or VHDL, but not both. If you buy a copy of the "real" deal, I believe you can use both. Both ALTERA and XILINX use ModelSim, so you can simulate and "see" your probable results in minutes. That way you can design and simulate each module as a confidence building measure before you integrate the, in this case, four modules.

You have the ability in either tool suite, to enter your design, simulate it, and program your target device. Once I figured out how to operate the XILINX tools, it took me about half an hour to get to where I could simulate my design of a long counter that reduced the on-board 80 MHz clock to 40 Hz. That's my backplane drive, and it's XOR'd with the 7-segment code to the LCD. Since I wanted HEX display capability, I had to build a new encoder. That took about 15 minutes including the 10 seconds to make a symbol of it so I could put it in a schematic. Figuring out how to program the device was not particularly difficult either. It took me two tries, about a minute each. The most time-consuming part of the exercise was writing the "user configuration file" which, among other things, defines the pin usage. IIRC, the whole job, from opening the box for the EVK to having the running exercise, took little more than an hour. Of course, I'd already figured out how to work the development tools. I did cheat a bit, as I'd been using VHDL to create testbenches for some time.

TO make an LED blink, you still have to generate a counter that divides the fast oscillator down to a rate that you can comfortably observe, and you have to prepare the UCF, though it would be a mite shorter. Since the counter would probably like to count at 1 Hz, that will blink the LED just fine.

If you want to make a LED blink, go ahead. This thing was my first VHDL exercise and I wanted to see whether I could make some use of all the features included on the evaluation board I'd purchased. When I was in college, nobody had thought of HDL's yet, and, in fact, the "transistor radio" was still fairly new, so I had to learn VHDL on my own. Since its popularity is increasing worldwide, while Verilog is used primarily in the U.S, and since VHDL is more "feature-rich," I figured it was a better choice.

For learning the HDL, it's probably easier to start with a CPLD in which you can "leave" your configuration without having to be connected to the PC-bound JTAG cable. That way you can work out, with a 'scope or whatever, anything you may have done wrong. You can build a pretty fancy state machine in a 72 macrocell CPLD, or two or more of them, running simultaneously.

You can do lots with the current FPGA eval kits, but they're often encumbered with devices that eat up pins you might want for something else, and often haven't enough of anything to allow you to do what you want. I'd recommend you read the fine print before buying an eval kit, not because they're expensive ... they're not ... but because of the confusion and disappointment that can result if you get one that's unsuited to your purpose.

For learning an HDL, the easiest thing is to get a low-cost CPLD eval board and work with that for a while. It won't have features on board that get in the way. I'd recommend the DIGILENT <www.digilentinc.com> XC2XL board (~$50). It even has a prototype area that you could use for your LED or whatever. You can buy the FPGA eval kit later, but I'd caution you to consider the expansion capability, i.e, what sort of connectors it has. If you have to use a dedicated connector, rather than a generic one, it can quickly become a pain in the gluteus maximus. Those older DIGILENT boards had 40-pin connectors compatible with discarded IDE cables. I've found them quite useable.

RE