icsp port design 3.3v system

[jmaudley]

Just trying to figure out what the voltage should be on pin 2 (vdd) of the ICD connector for my application using a 3.3v powered PIC18F26K80.

Should it be 3.3 or 5v?

My understanding is, that this pin powers the programming device (which also monitors the circuit voltage.

Also, my MCLR pin is pulled up to 3.3v.

Is there a possibility that the programming voltage could damage the 3.3v system?

The reason I'm using 3.3v is because I want to use an SPI display that is only 3.3v.

I could power the PIC at 5v and use open collector outputs and pullups but I thought making it all 3.3v might be a simpler solution.

[newguy]

Pin 2 is whatever your processor's Vdd is. What programmer are you using?

Years ago the CCS programmers (ICD-S and I think the first generation ICD-U) came with an internal jumper pre-wired so that the programmer supplied a 5V Vdd. With the jumper removed, connection of this 5V supply was disabled. For quite some time now their programmers default to NOT supplying Vdd.

[Ttelmah]

Key thing is the connections on MCLR. This pin has to go up to the Vpp voltage when programming. This is why the pull-up should be about 10K, so that excess current will not flow into the supply when this happens. From the data sheet:
"A suggested starting value is 10 k. Ensure that the
MCLR pin VIH and VIL specifications are met."

[jmaudley]

Thanks for the info. That confirms my assumptions.

I'm using a CCS ICD-U64 programmer.