18F67K40 MCLR

ertansuluagac · Joined: 13 Jul 2017 Posts: 135 Location: IZMIR

In the 18F67K40 processor, I want to use the MCLR input as input or output. Does this create a problem?
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Ttelmah · Joined: 11 Mar 2010 Posts: 19550

It can only be used as an input. From data sheet "RG5 is an input only pin".

It does also bring some issues.
First (obviously), if you want to perform ICSP to program the chip the
circuitry attached will need to be disconnected to do this.
Second, this pin does not have any protection on being taken above Vdd.
This is because during programming it is pulled up. If the circuit attached
ever allows it to go above Vdd, the chip can enter programming mode.
So the circuit you attach must provide protection against this.
For example, I've used the MCLR pin as a keyboard input on one circuit.
Had a protection diode to Vdd, and a jumper to disconnect this for
programming. Done like this it has happily/reliably worked.

temtronic · Posted: Fri Nov 29, 2019 6:03 am

I dedicate the ICSP pins for ONLY ICSP operation. Since I use the 18F46K22 for my projects, big or small, I've never run out of I/O pins yet. Last project though I used all but 2 !
As Mr. T says , if you do use it, you MUST protect it !