PIC18F65K22 MCLR pin connection?

[treez]

Hello,
We are using the PIC18F65K22 in our circuit with ICSP. Will it be ok to connect the programmer directly to the MCLR pin (pin 7) and then just have a 10K resistor from the MCLR pin to the 5V rail which supplies the microcontroller?

I realise that this is not what page 21 of the PIC18F65K22 datasheet says, but will it be ok?

PIC18F65K22 datasheet:
https://ww1.microchip.com/downloads/en/DeviceDoc/39960d.pdf

Basically, do you think that just having the 10K resistor connection, and no capacitor as shown on page 21, will result in noisy operation.
We do not actually wish to use the MCLR function.....ie, we don't need the micro to reset if it receives a low pulse on the MCLR pin.

 

[Venkadesh_M]

we don't need the micro to reset if it receives a low pulse on the MCLR pin.

It will work but not all times, Please follow the datasheet for best results.

 

[treez]

why shouldn't it work...?...I mean, with 10k pull up to 5V, the MCLR pin surely wont get accidentally reset?

 

[prabhukaran3]

Use 1K resistor.. sure it will work

 

[wp100]

Hi,

Just change your Config to Mclre = Off, that way the pin is free for the ICSP and the actual Mclre circuitry is then internally pulled up.

 

[treez]

Just change your Config to Mclre = Off, that way the pin is free for the ICSP and the actual Mclre circuitry is then internally pulled up.

Then we don't need any resistors or caps on the MCLR pin?

 

[betwixt]

It internally ties the reset signal to the VDD supply so it is always seen to be 'not reset'. It frees the pin but stops anything else externally causing a reset and you may have to be careful about supply rise time.

The reason for Microchip's suggested values is that the MCLR pin can be used to supply the programming voltage from the ICSP and allowing too much current to flow into the remaining circuitry through the pull-up resistor may overload the VPP supply and prevent reliable programming.

Brian.

 

[wp100]

It internally ties the reset signal to the VDD supply so it is always seen to be 'not reset'. It frees the pin but stops anything else externally causing a reset and you may have to be careful about supply rise time.

The reason for Microchip's suggested values is that the MCLR pin can be used to supply the programming voltage from the ICSP and allowing too much current to flow into the remaining circuitry through the pull-up resistor may overload the VPP supply and prevent reliable programming.

Brian.

Hi,

Thought you would be too busy finishing that roof to reply here :lol:

Been an exciting week for you, its really gone up as fast as you said !

Second fix and fittings done by next Friday ?

 

[betwixt]

Second fix and fittings done by next Friday ?

I have a fractured spine (car accident 30 years ago) so I left the roofing to the professionals. External and internal walls went up in 4 hours 20 minutes, the roof trusses took a day! I can't do the second fix until the roof is fully weatherproof, I have about 2,500 slates to go on yet but I have all the cables and pipes ready to go as soon as it's finished. Won't be long now.

The most irritating thing is I bought a new Tek MSO3000 series scope just before the work started and it's still in it's box! I'm suffering electronics withdrawal symptoms. :smile:

Brian.

 

[wp100]

I have a fractured spine (car accident 30 years ago) so I left the roofing to the professionals. External and internal walls went up in 4 hours 20 minutes, the roof trusses took a day! I can't do the second fix until the roof is fully weatherproof, I have about 2,500 slates to go on yet but I have all the cables and pipes ready to go as soon as it's finished. Won't be long now.

The most irritating thing is I bought a new Tek MSO3000 series scope just before the work started and it's still in it's box! I'm suffering electronics withdrawal symptoms. :smile:

Brian.

Hi,

Excuse us TreeZ,


Looks good how they have laid all the slates ready for fixing.

Tek MSO3000 series scope :-( and heres me thinking of updating my cumbersome 60mhz Hameg 604 from 1990 to one of the new Rigol 4 channel 1054Z, just divide your price by 10 !:lol:

 

[betwixt]

Slates are still in crates and out of camera shot. You will see them next week.

Helps having a step-daughter who is a Tek distributor in Croydon!

Brian.

 

[treez]

Great to hear it, sounds like a cracking building coming along!