PIC18F-LF1XK50 Datasheet, PDF (25/420 Pages) Microchip Technology – 20-Pin USB Flash Microcontrollers

2.11 USB Operation
The USB module is designed to operate in two different
modes:
• Low Speed
• Full Speed
Because of timing requirements imposed by the USB
specifications, the Primary External Oscillator is
required for the USB module. The FOSC bits of the
CONFIG1H Configuration register must be set to either
External Clock (EC) High-power or HS mode with a
clock frequency of 6, 12 or 48 MHz.
2.11.1 LOW SPEED OPERATION
For Low Speed USB operation, a 6 MHz clock is
required for the USB module. To generate the 6 MHz
clock, only 2 Oscillator modes are allowed:
• EC High-power mode
• HS mode
Table 2-4 shows the recommended Clock mode for
low-speed operation.
Note:
Users must run USB low speed operation
using a CPU clock frequency of 24 MHz or
slower (64 MHz is optimal). If anything
higher than 24 MHz is used, a firmware
delay of at least 14 instruction cycles is
required.
2.11.2 FULL-SPEED OPERATION
For full-speed USB operation, a 48 MHz clock is
required for the USB module. To generate the 48 MHz
clock, only 2 Oscillator modes are allowed:
• EC High-power mode
• HS mode
Table 2-5 shows the recommended Clock mode for full-
speed operation.
PIC18F/LF1XK50
 2010 Microchip Technology Inc.
Preliminary
DS41350E-page 25