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Nominal Voltage for PIC16F84A'S MCLR PIN

Hi there:


I'm designing a PCB for my robot project and I'm having some trouble with MCLR pin. Well, what I'm trying to do is set a jumper in the circuit so that the DC power supply does not interfere with the voltage comming from de serial connector when I'm programing It.

So far I managed to introduce the jumpers in the circuit but MCLR pin gives me a problem. The fact is that this pin acts as the mastereset during reproduction of the program and as a programming pin. So two different currents flow to this pin at different times. I decided to put two diodes (1N4007) so the current flows only in one direction to isolate  the programming circuiit form the reset circuit.

So there is a 0.7V decay on each diode. My question is if the diodes would affect the programming or the reproduction of th program.

I attach the schematic so that you have a better view of What I have done.


Dibujo.jpg90.63 KB

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The resistors in the above schematic are for isolation during programming.

With the circuit that i described in the previous comment i never had programming problem.

i usually do something like this http://www.piclist.com/images/boards/picmeter/correction.JPG but i don't use R2 and R1 is 10k

Ok, I see that with the Schottky Diode the voltage drop is less than with a normal diode, but: Does the voltage drop affect the programming at all?