I have questions relating to in-circuit programming for the PIC16F77.

* From what I understand the VPP pin must be tied to 12VDC+ during =
programming.

How do I isolate the VDD pins from this high voltage?

Is it recommended to use a diode between the VDD pin and VPP pin?=20

Or should I use a resistor?=20

If a resistor is recommended, what value is recommended?=20

* Do I need to power the PIC with +5VDC while it is being programmed =
(VDD, VSS pins)?

* When a PIC is in program mode (+12VDC on the VPP pin), what is the =
state of the I/O

pins. High impedance or output low?



Neil Gandler
Founder, CTO
MAI Technology Inc.
P.O. Box 64072
Sunnyvale, CA 94088-4072
Phone & Fax: 408-904-5089
e-mail: neil_gandler@getmai.com
http://www.getmai.com

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