Microchip Technology DM163025-1 Data Sheet

 2012 Microchip Technology Inc.

DS30684A-page 375

The USB module has specific clock requirements. For
full-speed operation, the clock source must be 48 MHz.
Even so, the microcontroller core and other peripherals
are not required to run at that clock speed. Available
clocking options are described in detail in 

.

The PIC18(L)F2X/45K50 has interrupt-on-change
functionality on both D+ and D- data pins. This feature
allows the device to detect voltage level changes
when first connected to a USB host/hub. 
The USB host/hub has 15K pull-down resistors on the D+
and D- pins. When the PIC18(L)F2X/45K50 attaches to
the bus the D+ and D- pins can detect voltage changes.
External resistors are needed for each pin to maintain a
high state on the pins when detached.
The USB module must be disabled (USBEN = 0) for
the interrupt-on-change to function. Enabling the USB
module (USBEN = 1) will automatically disable the
interrupt-on-change for D+ and D- pins. Refer to

 and

 for more

details.

Microchip provides a number of application-specific
resources, such as USB firmware and driver support.
Refer to www.microchip.com for the latest firmware and
driver support.