Lot of answers, I type slow too. Thanks guys!
First of all, I'm still little uneasy to connect +12V to MCLR given how my circuit looks like.
Looking at the pics of @jpanhalt I see that the second case clearly has Vpp and Vdd separated. In my case MCLR is connected to VCC (through 10k resistor) rail and VCC which also connects to Vdd of the PIC on the PCB. Wouldn't that cause the +12V from programmer side, put on the MCLR, to reach VCC and therefore Vdd of PIC (and other chips on the PCB)?
Looking at the first pic I can understand that the diode will prevent the +12V to creep into Vdd; and that is what my circuit is missing.
> Yes. The 12V on MCLR puts the chip in a different mode.
That explains why I'm not getting anything from the PIC so far..
> Note, the high voltage required to enter programming mode differs depending on the chip.
I checked:
Voltage on MCLR with respect to VSS (Note 2) ......................................................................................... 0V to +13.25V
The chip is also LVP capable, if configured as such AFAICT. The microc compiler configuration file I received along side the device and HEX binary suggests that the LVP bit is cleared and therefore the chip is not in the mood to perform low voltage programming. The PGM pin on the circuit is being used as a normal I/O pin, further suggesting that the LVP is indeed not available (as per the text attached).
> Microchip describes what is needed for those functions to work properly. If you have enough pins, it might be best to designate them as outputs and connect nothing to them.
True. They are not used for anything else but ICSP.
> If used as outputs that need to source significant current, that might not be the best solution. Jumpers/switches might be considered.
Yeah, I do not have the option to tinker with the PCB, or I would at least like to avoid it if possible.
> For 'fpicprog' to work with a HV programming only PIC, it would need a level shifter to drive Vpp with the appropriate programming voltage, under programmer control.
Right. I read the readme saying that was required ; I'll need to look into that now that I know MCLR needs to be at +12V.