MCF5272 Datasheet, PDF (294/550 Pages) Motorola, Inc – MCF5272 ColdFire Integrated Microprocessor Users Manual

Line Interface
A halted endpoint can be cleared in several different ways:
• CLEAR_FEATURE request with the endpoint halt feature selector set.
• A USB reset signal.
• A SET_CONFIGURATION or SET_INTERFACE request.
• On control endpoints, a SETUP token for the next request.
12.5 Line Interface
The recommended line interface is shown in Figure 12-24. The transistor used to control
the 1.5–kΩ pull-up resistor is optional.
3.3 V
1kΩ
GP I/O pin
MCF5272
100Ω
USB_D+
33Ω
USB_D-
33Ω
1.5kΩ±5%
Vbus
D+
D–
GND
USB
Series B
Receptacle
Figure 12-24. Recommended USB Line Interface
12.5.1 Attachment Detection
The USB specification requires that a pull-up resistor must be placed on the D+ signal for
the upstream hub to detect attachment of a full-speed device. The user may optionally want
to control the attach/detach detection by software instead of only at power on and off. With
software control of the pull-up resistor, the user has unlimited time to initialize the USB
module. The software controlled pull-up resistor can be implemented with only a few
discrete components. The recommended circuit for implementing software control of the
pull-up resistor is shown in Figure 12-24.
12.5.2 PCB Layout Recommendations
The device has input protection on all pins and may source or sink a limited amount of
current without damage.
12-34
MCF5272 User’s Manual
MOTOROLA