At 16:37 05.05.96 -0400, you wrote:
>I believe that E(E)PROM cells can also be erased by soft Xrays. The problem

My friend has done taht, well not with PIC (he doesnt own any) but with
normal OTP EPROMs from different manufacturers.

The hobbyist X-Ray machine he uses has following parameters:

Tube Voltage: 100,000V
Tube Current: 5mA
Distance from Collimmator: 5mm
Exposure Time: 20..120 min (in 10 min chunks)

As I did understand all brands of OTP (plastic, nonwindowed)
EPROM have been succesfuly erased. No harmful sideeffects
to devices.
Exposure time depends on brand and programming algorithm used.

I havent checked out whats about PIC, but I might give some
OTP PIC's for "testing"

I dont know about the power of the machine being used but I think
its WAY over what dentist use. The this X-ray machine was designed
to get snapshots in solid concrete up to 8 inches in depth. And it
is operating at maximum allowed power.

If I get any results on OTP PIC X-erasing I'll post to List.

...

The same guy with X-tube also checked beta radiation, but
that was really "soft" ie didnt have any erasing effect.
Success with X-ray was discovered befor going to gamma rad.

Some other people have tried EPROMS and OTP MCU (including PIC)
in a nuce reactor, but with bad results. All PIC's where destroyed
befor erasure. Only device being erased with radiation was i8751
and the device was slightly damaged.

FOLKS: PLEASE PLEASE dont try that at home!
alpha,beta,gamma radiation and X-rays _are_ harmful you know!

/antti sis@rasi.lr.ttu.ee