MDK-ARM Keil, MDK-ARM Datasheet - Page 114

• Manufacturer Part Number: MDK-ARM
• Description: KIT REALVIEW MCU DEVELOPMENT
• Manufacturer: Keil
• Type: Compiler and IDEr

Specifications of MDK-ARM

• For Use With/related Products: ARM MCUs
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

114
Chapter 5. RL-USB Introduction
These logical pipes are
implemented on the
serial bus as time
division multiplexing on
the USB network. Each
pipe can make a data
transaction within a
frame. The bus is
precisely defined into
1msec frames. Every
1ms the host PC sends a
Start-of-Frame (SOF)
token to define the 12 Mbit/s bus into a series of frames. Each pipe is allocated a
slot in each frame, so that it can transfer data as required.
USB supports several different types of pipes with different transfer
characteristics. This is in order to support the needs of different types of
application. It is possible to design a USB device capable of supporting several
different configurations. These can then be dynamically changed to match the
running host application. The types of pipes available are: Control, Interrupt,
Bulk, and Isochronous. All of these pipes are unidirectional, except the control
pipe that is bidirectional. The Control pipe is reserved for the host to send and
request configuration information to and from the device. Generally, the
application software does not use it. The unidirectional pipes are defined as
either IN pipes, which transfer data from the device to the host, or OUT pipes,
which transfer data from the host to the device. When a device is connected to a
USB network, it will always assume network address 0. The host uses a
bidirectional control pipe to connect to Endpoint 0. The host and the device then
go through an enumeration process. During this process, information about the
USB device is sent to the host. The host also assigns the device a network
address. This keeps address 0 free for new devices.
The remaining types of pipe are used solely for the user application. Typically,
within the USB peripheral of a microcontroller the physical Endpoints are
grouped as logical pairs. Endpoint 1 will consist of two physical Endpoints. One
is used to send data in to the USB host and one is used to receive data out from
the USB host.