mcf5272 Freescale Semiconductor, Inc, mcf5272 Datasheet - Page 294

• Manufacturer Part Number: mcf5272
• Description: Mcf5272 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

Line Interface
A halted endpoint can be cleared in several different ways:
12.5 Line Interface
The recommended line interface is shown in Figure 12-24. The transistor used to control
the 1.5–k) pull-up resistor is optional.
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
•
• A USB reset signal.
• A
• On control endpoints, a SETUP token for the next request.
CLEAR
MCF5272
SET
_
_
CONFIGURATION
FEATURE
Figure 12-24. Recommended USB Line Interface
GP I/O pin
USB_D+
USB_D-
request with the endpoint halt feature selector set.
or
100)
SET
MCF5272 User’s Manual
33)
33)
_
INTERFACE
1k)
3.3 V
request.
1.5k)±5%
Vbus
D+
D–
GND
USB
Series B
Receptacle
MOTOROLA