Datasheet

 2012 Microchip Technology Inc. DS30684A-page 351
PIC18(L)F2X/45K50
24.0 UNIVERSAL SERIAL BUS
(USB)
This section describes the details of the USB
peripheral. Because of the very specific nature of the
module, knowledge of USB is expected. Some
high-level USB information is provided in Section 3.14
“Oscillator Settings for USB” only for application
design reference. Designers are encouraged to refer to
the official specification published by the USB
Implementers Forum (USB-IF) for the latest
information.
24.1 Overview of the USB Peripheral
PIC18F2X/45K50 devices contain a full-speed and
low-speed compatible USB Serial Interface Engine
(SIE) that allows fast communication between any USB
host and the PIC
®
microcontroller. The SIE can be
interfaced directly to the USB by utilizing the internal
transceiver.
Some special hardware features have been included to
improve performance. Dual access port memory in the
device’s data memory space (USB RAM) has been
supplied to share direct memory access between the
microcontroller core and the SIE. Buffer descriptors are
also provided, allowing users to freely program end-
point memory usage within the USB RAM space.
Figure 24-1 presents a general overview of the USB
peripheral and its features.
FIGURE 24-1: USB PERIPHERAL AND OPTIONS
1kbyte
USB RAM
USB
SIE
USB Control and
Transceiver
P
P
D+
D-
Internal Pull-ups
External 3.3V
Supply
FSEN
UPUEN
USB Clock from the
Oscillator Module
Optional
External
Pull-ups
(1)
(Low
(Full
PIC18(L)F2XK50/PIC18(L)F45K50 Family
USB Bus
FS
Speed)
Speed)
Note 1: The internal pull-up resistors should be disabled (UPUEN = 0) if external pull-up resistors are used.
2: PIC18F2X/45K50 devices only.
Configuration
VUSB3V3
3.3V LDO Regulator
(2)
UOE
UTRDIS