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n00b ICD2 and MCLR question

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DanD

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So i have my ICD2 debugger board (USB and it is connected to my breadboard/project w/ the ICSP header. its wired up to my MC and is programming/debugging/working fine.

My question is how can i run the MC w/o using the ICSP supplied MCLR pin (VPP). i assume i should be able to unplug the ICSP VPP pin from the MC and just tie the MC's MCCLR/VPP up to 5V+ to run the MC normally? i also assume that i should NOT have both the ICSP's VPP AND 5+ at the same time. thatd be no good when it tries to program at 12V+. so i just wanted to make sure i'm doing that right i guess.

i wonder because it sort of seems like my MC doesnt work w/o the ICD2 hooked up
 
tie mclr to vdd with a small switching diode, cathode side to mclr ... this way, when vpp is applied, it will be blocked from your vdd rail by the diode.

this configuration works for me on the breadboard - there are other options as well, consult the microchip application notes for isolating an ICSP header.
 
^thanks i just read through it. i dont understand the resistor between VDD and VPP/MCLR.

my VDD is coming from my target's power supply and i assume VPP/MCLR is coming form the programmer's USB connection when connected. why the need to associate the two?
 
It is a pullup resistor. Among other things it allows the MCLR pin to be at a voltage other than Vdd without trying to fight your power supply.
 
right. so i see so id only need that if i hooked up my +5V pull from the targets supply PLUS the ICSP VPP pin at the same time. i wont ever do that so i should be ok w/o the resistor i think. right?
 
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