Programming a PICmicro without high voltage

[N9WXU]

I have an application using a PICmicrocontroller that cannot tolerate high voltage being applied to the circuit board for any reason.  I want to program the PICmicrocontroller in the final circuit.  Can I program a PICmicrocontroller without high voltage?

[N9WXU]

Sometimes it is not appropriate for voltages greater than VDD to be applied to a system.  For these cases, there is a low voltage programming option available on most of the PICmicrocontrollers.  The low voltage programming (LVP) option is triggered with a special LVP pin that must not be used for other functions.  The LVP pin triggers the same programming functionality typically caused by high voltage (VPP) applied to the MCLR pin.

LVP is enabled by default on all supported PICmicrocontrollers, but it can be enable/disabled by setting the LVPEN bit in a configuration fuse.

To use LVP you must:

1) have the LVP function enabled

2) configure your programmer to use LVP by setting the programmer options in MPLAB.

CAUTION: You can inadvertently disable LVP by releasing a HEX file with the LVP fuse disabled.  The only recovery method in this case would be high voltage programming.

NOTE: When LVP is enabled, high voltage is STILL enabled and can always be used.

Good Luck

[ric]

19 hours ago, N9WXU said:

...

The low voltage programming (LVP) option is triggered with a special LVP pin that must not be used for other functions.  The LVP pin triggers the same programming functionality typically caused by high voltage (VPP) applied to the MCLR pin.

Or triggered by holding the PIC in reset, and clocking a defined sequence into the chip via the PGD and PGC pins, so no extra pin is required.