• Please review our updated Terms and Rules here

DuPAL construction - has anyone made one?


Experienced Member
Dec 19, 2009
Hey, everyone!

Has anyone attempted to make a DuPAL to reverse engineer PALs?

I've got one built - and am pulling my hair out trying to get it programmed. I've tried reaching out on the Arduino forums (and not getting much help there yet - they wanted schematics and everything first), but in essence, it's a board that you build that runs on an Atmega328P running at 20MHz, and runs over a RS232 DB9 (with a MAX232). Really, that's it. You compile the boot loader to run at 20MHz and 56K, and install it over ISP (which seems to work - mine blinks 8 times like it's supposed to). Then, you compile the DuPAL binary, and do a "make program" with the system hooked over serial (after editing the makefile to put your serial port device), and it's supposed to upload with avrdude. Lastly, you put the PAL in, and run a small program on a PC to do the brute forcing of the PAL, and it controls the DuPAL with terse commands over serial.

But I'll be darned if I can get the actual DuPAL binary to upload over serial. I've tried different serial to USB cables - tried null modem adapters (which shouldn't be needed according to the pinout), tried using Windows vs. Mac. The boot loader seems happy - it's blinking 8 times. I've even tried replacing the MAX232.
Why don't you just flash the DuPAL binary directly into the Atmega? The Minipro EPROM programmer is able to flash AVRs out of circuit, and if you were able to flash Optiboot into the chip, you might as well flash DuPAL into the chip using the ISP interface.

(I have been using AVRs for a few hobby projects, and I never bother with a bootloader.)
I would be interested in seeing how this works, too. I have some S100 boards with locked 16L8's that I need to read. I was thinking of having a few boards made shortly. I need something for 20L10's too, but it looks like DuPAL hasn't been extended to use those yet.