Todd Peterson <PICLIST@MITVMA.MIT.EDU> wrote:

> >> Generally, the 16C57s erase in two to three minutes but I have
> >> not timed it exactly. This is the same with the other 5x devices
> >> but NOT so for most of the 16Cxx devices that can take 10 to 30
> >> minutes depending on the eraser and over 2 hours if the code
> >> protection is "ON."
>
> Really?  I've never had to go longer than 45 seconds with a
> PIC16C57.  I'm using a UltraViolet Products (UVP) eraser, and it
> seems to work very well. Usually I get a complete erase in 30
> seconds.

Todd and others:

The necessary erase-time for a particular EPROM is ONLY a function of
the intensity of UV light at the proper frequency that's impinging on
the die.

That intensity is governed by three factors:  The center-frequency of
your UV source and the shape of its frequency spectrum, the intensity
of the source, and (usually most important) the distance between the
source and the die.

Many UV erasers (e.g., the "Datarase" series that's so popular among
hobbyists) use relatively low-intensity bulbs but place the chips
right up against them.  Others (like the Spectraline erasers)
position the chips further away from higher-intensity bulbs...
There's a large difference in erase-times between those two devices.

In any case, the relative erase-times that were described for 16C5x
devices and 16Cxx devices are pretty accurate, and the newer parts
whose code-protect fuses are non-permanent DO take an incredibly long
time to erase.

-Andy

P.S.  Wait a minute.  I can see it coming, so before anyone asks...

      No, you CAN'T "over-erase" a PIC by leaving it in the eraser
      too long.

Andrew Warren - fastfwd@ix.netcom.com
Fast Forward Engineering, Vista, California
http://www.geocities.com/SiliconValley/2499