JDM issue 2 solved

Design Concepts
1

to people who were not able to burn a PIC18F452 yet:

Best Regards, Thorsten.

mbhp_jdm_lvp_fix.gif
mbhp_jdm_lvp_fix.gif500×513 34.9 KB

2

FYI: In the meantime two users who were not able to program a PIC18F452 before reported that this fix was the solution. They didn’t need an external power supply.

So please don’t forget to add the resistor if you want to burn a PIC18F

Best Regards, Thorsten.

3

Hey…

I’ve been burnin 16f/18f’s fine without any of these changes, this resistor fix for the 18f is not essntial is it? I mean, if an 18f is burnt fine on a jdm without these fixes and seems okay - it’s fine then right?

Best

Dan

4

I also burned a lot of PIC18F452 without this pull-down, but it seems that newer batches from the Microchip fab require it (there is nothing worst in logic design than floating input pins - maybe Microchip adjusted the process parameters and as a result the probability that this pin tends to logic-0 isn’t so high anymore).

However, you don’t have to burn the firmware again, this pin is only important to select the correct programming mode on a “virgin” or erased flash. Once the configuration data has been uploaded, the LVP flag is disabled and you don’t have to take care about it anymore.

Best Regards, Thorsten.