PIC18F-LF1XK50 Datasheet, PDF (251/420 Pages) Microchip Technology – 20-Pin USB Flash Microcontrollers

22.0 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 22.10 “Overview of USB” only for application
design reference. Designers are encouraged to refer to
the official specification published by the USB Imple-
menters Forum (USB-IF) for the latest information.
USB Specification Revision 2.0 is the most current
specification at the time of publication of this document.
PIC18F/LF1XK50
22.1 Overview of the USB Peripheral
PIC18F1XK50/PIC18LF1XK50 devices contain a
full-speed and low-speed, compatible USB Serial Inter-
face 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 22-1 presents a general overview of the USB
peripheral and its features.
FIGURE 22-1:
USB PERIPHERAL AND OPTIONS
PIC18F1XK50/PIC18LF1XK50 Family
3.3V LDO Regulator⁽²⁾
USB Clock from the
Oscillator Module
FSEN
UPUEN
P
P
Internal Pull-ups
Transceiver
FS
VUSB
Optional
External
Pull-ups⁽¹⁾
(Full
Speed)
D+
D-
External 3.3V
Supply
(Low
Speed)
USB Bus
USB Control and
Configuration
USB
SIE
256 byte
USB RAM
Note 1: The internal pull-up resistors should be disabled (UPUEN = 0) if external pull-up resistors are used.
2: PIC18F13K50/PIC18F14K50 only.
 2010 Microchip Technology Inc.
Preliminary
DS41350E-page 251