Hi Roger,

PIC devices have a good deal of protection built into their design.
There is the equivalent of Zener diodes on each I/O pin.
These “voltage clamps” help to protect the device from us.
The protection can handle a bit of “over voltage” caused, current (clamp current), but there is a limit.

The PIC12F675 has a limit of 20 mA output clamping current.
(Output clamp current, IOK (Vo < 0 or Vo >VDD) 20 mA).
Your schematic diagram shows R1 protecting the 12F675 HPWM Output pin (GPIO.5).
The protection depends upon the (over) voltage and the resistance value of R1.

-Adam-

Quote Originally Posted by PIC12F629/675 Data Sheet
Absolute Maximum Ratings PIC12F675
Voltage on VDD with respect to Vss -0.3 to +6.5V
Voltage on MCLR with respect to Vss -0.3 to +13.5V
Voltage on all other pins with respect to Vss -0.3V to (VDD + 0.3V)
Input clamp current, IIK (VI < 0 or VI > VDD) ± 20 mA
Output clamp current, IOK (Vo < 0 or Vo >VDD) 20 mA
Maximum output current sunk by any I/O pin 25 mA
Maximum output current sourced by any I/O pin 25 mA
NOTICE: Stresses above those listed under ‘Absolute Maximum Ratings’ may cause permanent damage to the device.
http://ww1.microchip.com/downloads/e...doc/41190c.pdf