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MCLR reset

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UnD3aD

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if pic12f683 mclr have Pull-up Resistor can i use this scheme to reset the pic?
 

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UnD3aD said:
if mclr have Pull-up Resistor can i use this scheme to reset the pic?

Yes, you could. Only problem is, as far as I am aware, the pics don't have a pull-up on MCLR.

Mike.
 
Pommie said:
UnD3aD said:
if mclr have Pull-up Resistor can i use this scheme to reset the pic?

Yes, you could. Only problem is, as far as I am aware, the pics don't have a pull-up on MCLR.

Mike.
You always need to add pull-up resistor to MCLR because PICs don't have internal pull-up on it. (Except when external MCLR is disabled, then the RESET input is held high by internal logic)
 
"A weak pull-up is automatically enabled
for GP3 when configured as MCLR and disabled when
GP3 is an I/O."
from datasheet
 
UnD3aD said:
"A weak pull-up is automatically enabled
for GP3 when configured as MCLR and disabled when
GP3 is an I/O."
from datasheet
Hmm that's a prety new feature... if you are correct, you won't need extra resistor.
 
HI UnD3aD,
you are right that as mentioned in the datasheet of the pic there is weak pullup when you configured the port in MCLR mode, but if you see on this page 38 of the datasheet where the internal structure of the port is given then you can see that between the pullup and MCLR pin there is an inverter and pullup is also mosfet the operation of which is dependent on the MCLR pin
and the basic purpose of using an external pullup resistor in any microcontroller ckt is to assure proper high logic level because reset pin is critical in any circuit operation.
So I will recomend you to use a pullup resistor
 
UnD3aD said:
"A weak pull-up is automatically enabled
for GP3 when configured as MCLR and disabled when
GP3 is an I/O."
from datasheet

The data sheet states,

An internal MCLR option is enabled by clearing the
MCLRE bit in the configuration word. When cleared,
MCLR is internally tied to VDD and an internal weak
pull-up is enabled for the MCLR pin.

This only applies to the internal MCLR. If you enable the MCLR pin then no pullup exists and you will need to add one. Why not just try it, you will find that your circuit will randomly reset.

Mike.
 
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