Chapter 33
Universal Serial Bus (USB) FS Subsystem
33.1 Chip-specific USBFS information
33.1.1 Universal Serial Bus (USB) FS Subsystem
The USB FS subsystem includes these components:
• Dual-role USB controller that supports a full-speed (FS) device . The module
complies with the USB 2.0 specification.
• USB transceiver that includes internal 15 kΩ pulldowns on the D+ and D- lines for
host mode functionality.
• A 3.3 V regulator.
• VBUS detect signal: To detect a valid VBUS in device mode, use a GPIO signal that
can wake the chip in all power modes.
USB controller
FS/LS
transceiver
USB voltage
regulator
D+
D-
VREGIN
VOUT33
Figure 33-1. USB Subsystem Overview
33.1.2 USB Wakeup
When the USB detects that there is no activity on the USB bus for more than 3 ms, the
ISTAT[SLEEP] bit is set. This bit can cause an interrupt and software decides the
appropriate action.
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
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