RE: Software/info wanted

From: Baltissen, GJPAA (Ruud) (
Date: 2003-11-03 08:23:06

Hallo Groepaz,

> > It is doable but a hell of a job. And not worth the 
> > trouble IMHO.
> thats why you use a computer for can probe all 
> possible combinations very quickly :o)

I'm sorry for not being that precise; I meant soldering the hardware.

> (you may add some electronics to
> keep current low on the pins used for probing if in doubt)

Unfortunately that is only part of the problem. The Dela tester can test up
to 20 pins TTL-ICs. It expects GND on the right bottom pin. Then it has 3
transistors onboard to supply Vcc. Haven't checked it but I guess it only
can test 14 16 and 20 pins ICs. 

To be able to test 4164 DRAMs for example you need a device that can supply
GND to pin 16 and +5V  to pin 8. A normal TTL output won't do so you need at
least two transistors to supply Vss or Vcc for these pins. Better: for all
pins. This enables you to test all kind of weird ICs. IIRC there is a TTL
serie that has the powersupplies in the middle of the IC. Anyway, you need
two signals to steer those transistors plus one to read the pin in case it
is an output. 
Now add the circuitry that enables you to find out if a pin is in- or
output. I haven't given it a big thought but IMHO you need at least tw extra
signals to steer the analogue part of that circuit. Meaning we end up with a
lot of hardware :(

Some years ago I started building a 40 pins IC-tester using five 8255's: one
8255 for every 8 pins. The project never ended because I lost it :( That is,
I put it somewhere and have no idea at all where. But one of these days I
plan a big reorganisation of my room and other places and I hope it will
show up.

   / __|__
  / /  |_/     Groetjes, Ruud
  \ \__|_\


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