Chapter 12. Universal Serial Bus (USB)
12-35
Line Interface
12.4.7 Endpoint Halt Feature
USB has the ability to halt endpoints due to errors. The user is notified when an endpoint
is halted and when the halt is cleared. When an endpoint is halted, the user should abort the
current transfer and reinitialize the FIFO for the endpoint. An endpoint can be halted for a
variety of reasons.
•
SET
_
FEATURE
request with the endpoint halt feature selector set.
•
EPnCTL[STALL] is set by the user. This bit should be set only when there is a
critical error on the endpoint.
•
On control endpoints, an error processing a request.
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–k
Ω
pull-up resistor is optional.
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
GP I/O pin
USB_D+
USB_D-
USB
Series B
Receptacle
Vbus
D+
D–
GND
3.3 V
1k
Ω
100
Ω
33
Ω
33
Ω
1.5k
Ω
±5%
MCF5272
Содержание DigitalDNA ColdFire MCF5272
Страница 1: ...MCF5272UM D Rev 0 02 2001 MCF5272 ColdFire Integrated Microprocessor User s Manual ...
Страница 38: ...xxxviii MCF5272 User s Manual TABLES Table Number Title Page Number ...
Страница 58: ...1 10 MCF5272 User s Manual MCF5272 Specific Features ...
Страница 90: ...2 42 MCF5272 User s Manual Exception Processing Overview ...
Страница 96: ...3 6 MCF5272 User s Manual MAC Instruction Execution Timings ...
Страница 158: ...5 46 MCF5272 User s Manual Motorola Recommended BDM Pinout ...
Страница 184: ...7 12 MCF5272 User s Manual Interrupt Controller Registers ...
Страница 338: ...13 44 MCF5272 User s Manual Application Examples ...
Страница 414: ...18 6 MCF5272 User s Manual PWM Programming Model ...
Страница 452: ...19 38 MCF5272 User s Manual Power Supply Pins ...
Страница 482: ...20 30 MCF5272 User s Manual Reset Operation ...
Страница 492: ...21 10 MCF5272 User s Manual Non IEEE 1149 1 Operation ...
Страница 548: ...INDEX Index 12 MCF5272 User s Manual ...