xpyttl wrote:
"Ken Scharf" wrote in message
...


diode from MCLR to VSS (Anode to VSS) and that brings the 'zero'
voltage down to -.37v or so.


You may want to check the datasheet for the specific part you are going to
use. the 16F628 datasheet, for example, specifies the absolute minimum
voltage on MCLR at -0.3v. Ditto with the 877 and 84A.

..


I could put a germainium or low voltage drop si in series with
the VPP to block the negative voltage all together. That would
somewhat limit the vpp, which might be a problem.