Any manufacturer ever come out with something like this? There are lots of old parts that are impossible to get. With all the configurable parts available these days, some sort of 1000 gate configurable part in a few different DIP packages (in addition to modern packages) would be extremely helpful for fixing old stuff of dropping a bit of exact logic exactly where you need it. Or am I totally high on this idea?
What you are after is called a "CPLD" - Complex Programmable Logic Device. It's like the little brother of the FPGA or ASIC. It's a device with no set function, but you program the logic into it.
You can also emulate logic using an EPROM or EEPROM - program it with a lookup table to give the right results on the data bus depending on the inputs to the address bus.
Using ROM (EEPROM) as programmable logic:
I think a PAL Devices closely match this function.
This is one example of such a device:
http://www.ti.com/lit/ds/symlink/tibpal16r8-25c.pdf
http://uk.farnell.com/texas-instruments/tibpal16l8-25cn/ic-pal-16l8-3-state-25ns-20dip/dp/1610184
They are 20pin dip packages which can be programmed to serve this sort of function. Also, their VCC/GND pins are in the same place as the 4000 series devices.
I didn't think they still made those babies.
Here is a CPLD and CPLD programmer all packaged as an Arduino Shield, http://amani64.com/amanigthw.htm
and they have some tutorials for it; http://amani64.com/learning.htm
I just saw one of those pal things on a board from 1987, are they resusable?
I'm not entirely sure. By the looks of things they are programmed with an additional +10v supply, which suggests it should be possible to reprogram each fuse. I managed to find the programming algroithm template for these devices:
http://www.ti.com/download/hirel/apps004.txt
Edit:
On second thoughts, they are not. The logic lines are wired together by a series of fuses. To program it, the connections that are not wanted have their fuse 'blown'. Which means they cant be reprogrammed (unless the new program requires the same fuses to be blown and maybe some others).
Yeah I looked up the datasheet and saw that crazy chart of fuses, quite the hassle it seems
majenko:
What you are after is called a "CPLD" - Complex Programmable Logic Device. It's like the little brother of the FPGA or ASIC. It's a device with no set function, but you program the logic into it.You can also emulate logic using an EPROM or EEPROM - program it with a lookup table to give the right results on the data bus depending on the inputs to the address bus.
Oh, I realize that. I actually reinvented that wheel when I did a little project that converts binary to BCD so I can get output on 7 segments. My solution was to use a 3 64Kx8 EEPROMs as a lookup to map the binary (16 bit) value into BCD (5 digits * 4 per digit = 20 bits or 1M). Then I found out it was a pretty standard technique (though not, obviously, for a lookup table this size. my solution is insane). . Also then learned (both from TTL Cookbook) how to use the 150 or 151 to make any function of 4 or 5 bits.
That's a pretty ugly board:
The issue is that it's an EPROM, it's in it's own package, you can't use it to replace a part that is a 16-DIP or whatever particular package that it is in, not without a lot of hacking. I was wondering if this was supplied in the proper packages (i.e. 14/16/18 DIPs especially) that could be used to create that functionality.
Yeah, lot of parts there for something that could be easily controlled with a '328P chip, a UNL2003 (common cathode) or UDN2981 (common anode), and multiplexing in software. Or with 2 added shift registers if you didn't 13 or 14 (with decimal point) IO pins tied up.
CrossRoads:
Yeah, lot of parts there for something that could be easily controlled with a '328P chip, a UNL2003 (common cathode) or UDN2981 (common anode), and multiplexing in software. Or with 2 added shift registers if you didn't 13 or 14 (with decimal point) IO pins tied up.
Oh, I totally know. And the TTL based output board can only translate 16 bit numbers. At the time I wanted to understand logic chips. I set some goals for simple stuff, including this, an adder, a multiplier using 284/285 chips, the reverse of it (input board) using BCD switches and EPROMS to change the BCD to binary, and that little text scroller in pure TTL that I posted a while back. Lately I have been using the Arduino and writing more code than laying wires down. They are both interesting. I did update this to using Arduino, both data entry and output and I can use my existing arithmetic boards with either the TTL input/output boards or the microcontroller based ones. And the Arduino board does 32 bit unsigned ints.
I think you can still get GAL16v8 and similar in 20pin DIPs, but that's about the smallest. Go to digikey and search for "PLD" and adjust the parameters....
Small microcontrollers are cheaper, lower power, and more general purpose, though they're slower for basic logic functions. A PIC16F505 (dip14) is less than a buck; I've often thought it would be interesting to write software to permit such chips to implment traditional PAL/GAL logic (slowly.) Some of the newer PICs have some programmable logic built into them, that might allow higher speed fuctions ("Configruable Logic Cell" or CLC)
There are also the very tiny Silego "GreenPak" devices (8 and 12 pin "mixed signal arrays") that seem really cool, but probably aren't what you're looking for.
There are lots of old parts that are impossible to get.
You haven't looked in my garage.
Don
LOL
floresta:
There are lots of old parts that are impossible to get.
You haven't looked in my garage.
Don
74185s?
If you are willing to part with them let me know...
I didn't see any 74185's in my initial cursory look. I'll do a more thorough check later on.
If you want to try and substitute some 6SN7's I know can find those.
Don
floresta:
I didn't see any 74185's in my initial cursory look. I'll do a more thorough check later on.If you want to try and substitute some 6SN7's I know can find those.
Don
I was half kidding, there is like one guy on eBay with these and he wants $20 each for them. I guess they never made that many. It's a binary to BCD converter, I wouldn't have been surprised to see them in old pinball games or something like that but I guess not so much.
As far as 6SN7s, I don't know what those are off the top of my head. This is all I found when I looked just now:
How does this vaccuum tube help me replace a binary-to-BCD TTL chip other than using a room full of them?
How does this vaccuum tube help me replace a binary-to-BCD TTL chip other than using a room full of them?
The 6SN7 is kind of like the vacuum tube version of the 'universal gate'. You can build up any logic function if you have enough of them, probably only a room full if it is a very large room.
Don
floresta:
How does this vaccuum tube help me replace a binary-to-BCD TTL chip other than using a room full of them?
The 6SN7 is kind of like the vacuum tube version of the 'universal gate'. You can build up any logic function if you have enough of them, probably only a room full if it is a very large room.
Don
I see on Wikipedia that they built the ENIAC out of them. I could probably get an article on Wired if I built my own computer out of them.