On Wed, 14 Mar 2001 04:14:57 -0800, you wrote:

>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.
Yes
>How do I isolate the VDD pins from this high voltage?
By not connecting MCLR to VDD !
>Is it recommended to use a diode between the VDD pin and VPP pin?=20
No
>Or should I use a resistor?=20
Yes, if you would otherwise be connecting MCLR/Vpp to Vdd
>If a resistor is recommended, what value is recommended?=20
Needs to be low enough to not cause spurious noise to cause a reset,
and high enough not to load the programmer. 10K would be a good guess.
>* Do I need to power the PIC with +5VDC while it is being programmed =
(VDD, VSS pins)?
Yes.
>* 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?
High Impedance
>
>
>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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