I've only got the answer for 16c74, but is approx. 20K as you remember.
Actually, it is specified as a current, between 50 and 400 uA, with 250
being typical. (Divide it into 5V to get apparent resistance)

And as for that confounded protection bit - there is an article on the web -

http://www.cl.cam.ac.uk/users/rja14/tamper.html (which I have read)

but it doesnt really touch the subject of OTP devices except by saying that
there are clever (but expensive) ways of finding out what's stored in the
most common of ICs - and they managed to copy a 386 processor assuming only
a knowledge of the basic layouts of e.g. transistors in silicon.

It would seem that if you enter the commercial market BIGTIME you are going
to see copies of your devices ASAP - provided someone REALLY wants them.

If it is your code you want to proctect - don't bother - give them the HEX
file and hope the guy is just lazy enough to figure out exactly how it
works. I've learnt that you should NEVER NEVER NEVER underestimate a
hacker's time and patience. (I'm reformed now.)

If I am wrong, can someone please enlighten me as well.


At 01:09 PM 12/17/96 PST, you wrote:
>Hi everyone!
>     I am asking what is the rough value of the weak pull-ups (I think it's
>about 20K) but I cant remember.  Can anyone out there tell me? (The device I
>am using at the moment it a 16C84)
>Also, this business about the busting of pics.  Is there any pic (probably
>an O.T.P. device) which will not let you look at what is inside it?  No
>matter what you do to it (putting in the microwave etc!)
>
>Thanks in advance,
>     Brian.
>
>

Jan van der Watt
[i SAW Elvis. He sAt BETween mE anD BigFOOt on THE uFo.]