MDK-ARM Keil, MDK-ARM Datasheet - Page 116

• 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

116
Chapter 5. RL-USB Introduction
Bandwidth Allocation
The USB protocol is a master slave protocol so all communication is initiated by
the host. Therefore, it is up to the host to determine what pipe packets are
contained in each USB frame. Any ending Control and Isochronous pipe packets
will always be sent. During enumeration, any interrupt pipes will specify their
required polling rate. Any remaining bandwidth will then be available for use by
Bulk pipes. The host must also manage the loading of the USB network when
multiple USB devices are connected. Control pipes are allocated 10% of the total
USB bandwidth. Interrupt and Isochronous pipes are given 90%. Bulk pipes use
any idle periods on the network. These are maximum allocations; so on most
networks there will be plenty of unused bandwidth. If a new device is connected
to the network, the host will examine its communication requirements. If these
exceed the bandwidth available on the network the host will not allow it to join
the network.