Endpoints behave as a group of FIFOs. Enumeration takes place anytime the bus is started or a device is plugged into or unplugged from the bus. These packets inform the sender of the data as to the condition of the received data packet. Device's endpoint is incapable of receiving or sending data. This requires host intervention.
Hubs are responsible for the removal and addition of USB devices.
They detect the addition of a USB device and inform the host to enumerate the device. Also, hubs are responsible for the power control of the devices under them. The '930 is based on MCS 251 processor core and the '931 is based on the MCS 51 core. An interrupt transfer has a service interval from 1 to 255 ms. Interrupt transfers can send a maximum of 64 bytes per packet.