Datasheet

 2009-2018 Microchip Technology Inc. DS30009960F-page 51
PIC18F87K22 FAMILY
To use the reference clock output in Sleep mode, both
the ROSSLP and ROSEL bits must be set. The device
clock must also be configured for an EC or HS mode. If
not, the oscillator on OSC1 and OSC2 will be powered
down when the device enters Sleep mode. Clearing the
ROSEL bit allows the reference output frequency to
change as the system clock changes during any clock
switches.