# Just getting started in the world of Digital Circuits

#### TigerLeep

Joined Oct 20, 2011
2
I'm an experienced software developer (Assembly, C, C++, VB, C#, ...) and am just starting to get into the world of digital circuit design. I'm 210% fascinated by it and am learning at a very rapid pace. I wanted to start playing with breadboarding some simple circuits (adders, muliplexors, etc) using logic gate chips as a means of learning, but I know I will quickly outgrow simple breadboards. A friend suggested I look into FPGAs and so I did. They look like they may be the perfect "playground" for me to learn with, but there is an overwhelming amount of information to learn before I can decide which to get. So I guess I'm hoping for some beginners advice. Tips, suggestions, where to start, etc.

I've looked at VHDL and Verilog syntax, and even though I have a strong C style background, I'm leaning more toward VHDL. It seems (to me at least) to be closer to "circuit design" than Verilog's "c" like syntax. I've only seen a few YouTube videos on both though, so it's a very un-educated assumption at this point.

Money isn't TOO much of a concern (I'm ok with spending several hundred on an FPGA, but I'm not willing to spend thousands). I know I'd like something with a lot of (forgive me if I have any terminology wrong, still learning rapidly) logic units, and PROM would be nice so it could retain its programming without power. I don't really know what I want for inputs/output/ports/etc... When I was originally thinking of just breadboards and Radio Shack logic gates, I was probably going to use switches and LEDs. Now I see FPGAs with VGA and HDMI out and built-in character displays and USB and PCI ports and... As I said, quite overwhelming.

Maybe it might help to know that my immediate long-term goal (was that an oxymoron?) is to make a CPU (strictly as a learning project). I've been doing a LOT of learning on the architecture of CPUS. I'm not talking about anything anywhere CLOSE to as complex as, say, an Intel I7. I'm talking 8-bit bus, simple adder, simple instruction set, probably only 1 accumulator... all as a learning process. Will probably expand on it as I learn and improve it over months/years once I get it made initially. The FPGA is the next step in that learning process, so I can start actually playing for real instead of in a simple Hardware Simulator (worked though the book The Elements of Computing Systems by Noam Nisan and Shimon Schocken... Unbelievably good book).

I'll stop rambling now. I can't wait to hear what kind of feedback I get from the community here!

#### BillO

Joined Nov 24, 2008
990
A development board based on Xilinx or Altera chips would be a starting point. They both offer free development environments.

Go to eBay and search on FPGA development or CPLD development. You'll see hundreds of options starting at under $20. Of course, if money is no object, both of these companies offer their top of the line chip development environments in the$15K+ range!!! Some of these chips are more than the price of a small car.

I have and Altera UP-2 board that has both an FPGA and a CPLD on it along with some switches, push buttons, LEDs and 7-segment displays. As well, all the chip pins are broken out to pin sockets. You can get this for about \$100 if you look, but the chips are a little outdated.