PAL16L8ACN

Lyos Gemini Norezel · Post by **Lyos Gemini Norezel** » Fri Apr 23, 2004 7:06 pm

Hey Ya'll... I managed to rescue 17 IC chips marked PAL16L8ACN and I can't find the datasheets for these anywhere. Could anyone tell me what the heck these things are? What they're used for? Perhaps even how to program them? Any help would be apprieciated. Thanks.
Lyos Gemini Norezel

8BIT · Post by **8BIT** » Fri Apr 23, 2004 7:33 pm

They are Programmable Array Logic chips. You can find more info about them by looking at a data sheet for a PAL16L8 from Jameco's web site. Here is the link:
http://www.jameco.com/Jameco/Products/ProdDS/28020.pdf

Hope this helps.

Daryl

Lyos Gemini Norezel · Post by **Lyos Gemini Norezel** » Sun Apr 25, 2004 6:12 am

Thanks Daryl.... that helped alot... now if only I could figure out how to make a PAL programmer that works from a computer... any ideas?
Lyos Gemini Norezel

orac · Post by **orac** » Wed Apr 28, 2004 4:53 pm

Hi Everyone,

Note, the last time that I checked, the 16L8 wasn't reprogrammable.
This means that if it was already programmed you might not be able to program it again. Please check the data sheet.

Cheers,

Paul

Lyos Gemini Norezel · Post by **Lyos Gemini Norezel** » Thu Apr 29, 2004 6:01 am

Of course... I shoulda known that... anyone know a good way to do a hex dump on these? I'm using an HP 4100 series laptop with a messed up serial port... so parallel or usb is best. Any ideas?
Lyos Gemini Norezel

John West · Post by **John West** » Fri Apr 30, 2004 1:26 pm

The 16L8 has no internal state, and few enough inputs that it's practical to wire up switches and LEDs and write the truth table by hand. I did that once in my previous job: we'd run out of pre-programmed devices, and the company that made the equipment we were servicing no longer existed.

If they were "rescued" from boards, they will already be programmed. Unless they happen to be programmed in a way that you can use, they'll be useless.

Lyos Gemini Norezel · Post by **Lyos Gemini Norezel** » Sat May 08, 2004 4:01 am

John West wrote:

The 16L8 has no internal state, and few enough inputs that it's practical to wire up switches and LEDs and write the truth table by hand. I did that once in my previous job: we'd run out of pre-programmed devices, and the company that made the equipment we were servicing no longer existed.

I imagine I could figure out the circuit and even write the results... but I would be utterly lost as to how to read it. I don't know binary and am only beginning with assembly.

Quote:

If they were "rescued" from boards, they will already be programmed. Unless they happen to be programmed in a way that you can use, they'll be useless.

I rescued them from a store that specializes in ancient computer stuff (among other things) they came in a plastic IC holder that contained 17 of these chips. They don't look like they've ever been used... but then again looks can be decieving. Any ideas on how to do a hex dump on these chips and then have the hex converted to assembly?
Thanks
Lyos Gemini Norezel

erd · Post by **erd** » Sat May 08, 2004 4:21 am

Lyos Gemini Norezel wrote:

Any ideas on how to do a hex dump on these chips and then have the hex converted to assembly?

PALs are not like ROM chips - yes they are programmed devices, but the programming is a representation of logic equations, not machine code. PAL stands for "Programmable Array Logic".

PALs are used to replace a handful of generic TTL logic chips (7400, 7404, 7474, etc.) with a single part, one that could be quickly replaced if the logic ever needs to be changed. Older ones, made in the 1980s, use fusible links and can only be programmed ("blown") once. Newer devices, called GALs (Generic Array Logic) are based on EEPROM-like cells and can be reprogrammed a number of times. Also, PALs were made in certain hardware configurations with descriptions like "10H8" or "12L2" - the first number is the number of inputs, the letter is High or Low-true outputs, and the last number is the number of outputs. Therefore, a "12L2" has 12 inputs, and two low-true outputs. GALs do not have predetermined inputs or outputs. A 16V8 GAL has up to 16 inputs and up to 8 outputs. You can feed it a set of equations with 2 inputs and 8 outputs or vice versa - whatever you need.

They are useful for building address selectors for implementing a memory map on a processor - you could literally take A8-A15 from a 6502, and program the GAL to output chip selects for up to 8 address ranges anywhere in memory, on a page boundary. If you needed to determine chip selects for more than that, you could go with a larger GAL (like a 22V10) or chain two 16V8s together.

They are very handy little devices and can save a lot of work in building small computers. The fact that some of your logic isn't written in stone can allow some pretty creative results.