On Tue, 17 Dec 1996, Clewer,Brian wrote:

>      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)

They're not exactly resistors - according to the databook they have very
small geometry P-channel FETs, so the output current will have a resistive
slope at low voltage (across the FET, hence output near Vcc) switching to
approximately constant current output at some point.  The pull up is only
rather loosely spec'd - I think I recall a figure of 200uA max, but I
can't find it in the databook right now.

> 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!)

If you can throw sufficent time and money at it, certainly not.  To
protect it from casual amateurs?  It varies, and there will likely never
be a truly authoritative answer in the affirmative, as it's deucedly hard
to prove a negative.