Reset Circuit and ICSP

[haxan]

Hi, i am trying to find out the perfect way to reset a PIC18 microcontroller other than having to use an IC for it.

Secondly, how can i make my circuit complaint for ICSP and somehow isolate it from the circuit.

Is it possible to program a PIC even if the LVP is disabled?

 

[Nigel Goodwin]

Hi, i am trying to find out the perfect way to reset a PIC18 microcontroller other than having to use an IC for it.

If you're NOT using ICSP, then connecting directly to Vdd is perfectly fine. It's covered in the datasheet.

Secondly, how can i make my circuit complaint for ICSP and somehow isolate it from the circuit.

For ICSP connect MCLR via a diode and resistor to Vdd. For the other pins, choose what you use them for carefully.

Try reading the instructions with the PICKIT2 which shows you what to do.

Is it possible to program a PIC even if the LVP is disabled?

Yes, perfectly possible and common, LVP is RARELY ever used, and seems a mostly useless feature (it's too wasteful).

 

[haxan]

If you're NOT using ICSP, then connecting directly to Vdd is perfectly fine. It's covered in the datasheet.

Nigel in datasheet i can only find this circuit (as attached).

I want to add a push button there as well. Should i replace the diode with a push button connected to ground? Also the value of C (capacitor) of 10uF will be fine?

 

[Pommie]

Just place the push button across the capacitor.

Mike.

 

[haxan]

wont it just shorten the capacitor each time i press it causing a sudden discharge which might damage the capacitor. If not then which cap value is ok 4.7uF, 10uF ?

 

[Sceadwian]

If I'm not mistaken the cap value is just to eliminate high frequency noise resetting the MCU during dips, the value doesn't need to be nearly that high.