MCLR pin of micro has ESD diodes in it?

[treez]

Hello,
Is it true that the PIC18F65K22 does not have an internal ESD diode from its MCLR pin to its VDD pin?
We are running this micro off of a 3V3 rail, and wonder of we can just put in a 5V signal directly into its MCLR pin, (pin 7) with no series resistor? (this 5V signal is from the output of a 5V regulator)

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

 

[FvM]

Raising MCLR above VDD won't damage the chip but enables programming mode. I guess that's not what you want to achieve.

 

[treez]

thanks, yes, , but as you know, I am not speaking of programming mode here...so I wonder if raising the mclr pin above vdd makes some of the pins go randomly output high or low?......I am pretty sure that when the mclr pin is raised above vdd, all the pins are supposed to go high Z..but they actually don't, (due to a known malfunction with microcontrollers) , they go randomly output high or low....(I know this because you can sometimes here connected relays chattering as the ports misbehave as described.

 

[wp100]

thanks, yes, , but as you know, I am not speaking of programming mode here...so I wonder if raising the mclr pin above vdd makes some of the pins go randomly output high or low?......I am pretty sure that when the mclr pin is raised above vdd, all the pins are supposed to go high Z..but they actually don't, (due to a known malfunction with microcontrollers) , they go randomly output high or low....(I know this because you can sometimes here connected relays chattering as the ports misbehave as described.

Hi,

Mystified ??

Raising Mlcre pin by +1.5v over VDD is the minimum needed at activate VPP , so as FVM says at 5v Mclre , the chip will possibly enter programming mode.

Sounds like you have tried it with you saying the relays are chattering , but more likely its the program being restarted and stopped by the Mlcre being in an almost floating condition between run and Vpp mode

Are you trying to turn the whole chip into some form of tri-state condition, to what end. ?

 

[treez]

on one of our boards, there is an external connection to the mclr pin, it is from a 5v rail, and gets switched onto the mclr pin of the micro, and the micro's vdd pin is 3v3....it is the reset function.......so they can reset the micro.....but I reckon they have got this wrong, as they will just inadvertently put it into programming mode or something