What do you need to use the PLD (ATF16V8)

What is a PLD?

The key to this module’s compactness is a “Programmable Logic Device” (PLD). Some people call them “PAL” or “GAL” instead. These chips don’t do anything out of the box; they contain a collection of “cells”, each cell containing a flip-flop and a few gates. Using a compatible programmer (many EEPROM programmers will do the trick), you can interconnect those existing components to create different behaviours, and map them into different input/output pins.

What do you need to use them?

Hardware: To “configure” a PLD, you need an EEPROM programmer that supports this chip. Not every EEPROM programmer does; in particular, Arduino-based programmers can’t write PLDs. I’m using a T48, the successor of the popular TL866-ii+; both are relatively cheap and can write these PLDs. The instructions below assume you have one of those.
Software: You need two main pieces of software. The first one transforms some definitions describing what you want the chip to do into a cell interconnection that can be “burned” into the chip. The output of that is a “.jed” file. Then, you can use software specific for your programmer to burn the .jed file into the device.
- I use Atmel’s “WinCUPL” software, which generates the JED file. Other alternatives include PALASM (very old!), GALasm (non-commercial use only), and Galette (which has been intermittently unmaintained but seems to be active as of April 2024). These use very different syntaxes to specify the logic definition.
- For the T48 or TL866, the manufacturer-provided software can do this, although I use minipro (Note: I added the T48 support in minipro, and it is still experimental, but it seems to work for me).
- Shortcut: If you have the JED file and don’t plant to change it, you can skip the compilation and go straight to programming. The JED file for my module is here (follow the link and click the download button).

WinCUPL

Atmel, owned by Microchip makes the ATF16V8. The chips are supported and still manufactured. Microchip has a philosophy of rarely stopping to make old parts, so designs relying on their ICs can keep being maintained. However, there’s not a lot of effort in improving the software support features. The official software for using older PLDs is called WinCUPL and can be downloaded for free from Microchip’s website; it asks for a license number, but there’s a free one on the download page itself.

WinCUPL is very old, has a UI that looks taken out of the ’90s (because it probably is), and includes an IDE that’s extremely unreliable: For me, the syntax highlighter messed up the colours of my code after a bit of edition, and it crashed after every compile to JED (the compile worked but then the IDE closed itself). So I avoid it like the plague.

However, when you install it, you get some command line tools that are actually quite reliable. It also comes with several example files to help you understand how to design the logic formulas that get translated to cell interconnects. I’ve run it in Windows 10 and Linux (through the WINE emulation layer), and it works ok. You’ll need to be familiar with a command line.

Installing it is relatively straightforward. By default, it goes into c:\Wincupl. If you have a cupl file like the one for this project, you can build it with this command:

c:\wincupl\shared\cupl.exe -j -u c:\wincupl\shared\Atmel.dl be8clock.pld

Or in Linux:

wine 'c:\wincupl\shared\cupl.exe' -j -u 'c:\wincupl\shared\Atmel.dl' be8clock.pld

If your file is correct, you will get a be8clock.jed file.

minipro

minipro is an open-source programmer that’s compatible with the TL866 family of devices by xgecu (including the T48 and T56). These reasonably priced, widely available devices support a wide range of ICs.

If you have it, you can install minipro (check their webpage for up-to-date install instructions), insert the ATF16V8 in the device, and write the JED file with the following command:

minipro -u -w be8clock.jed -p ATF16V8B

After minipro writes the cell configuration into the chip, it will verify. If verification fails, check if you’re using the right IC (see below) and that there are no compilation issues with your cupl file. Don’t use the misconfigured PLD. A badly written PLD could have an internal invalid configuration that shorts itself or overheats, and you may end up damaging the PLD or other components.

Using a different PLD

There are a few variants of the 16x8 PLD that are slightly different. Most will support this project but may have different programming algorithms. Check the following if you are using a different device:

The cupl file has a “device” line that I’ve set to g16v8a. If your device is different you may need something else here. The WinCUPL buggy IDE has a list of devices and specifies for the chip name what’s the corresponding “device” label that you required in the CUPL file.
Different variants may need different programming algorithms or voltages. minipro may require you to change the -p ATF16V8B to something else. Check the output of minipro -l to see if your device is listed.