Browse Prior Art Database

A Means To Reliably Determine The Steady State Of A USB Plug-and-Play System

IP.com Disclosure Number: IPCOM000014193D
Original Publication Date: 1999-Nov-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Phuc Do: AUTHOR [+3]

Abstract

A Means To Reliably Determine The Steady State Of A USB Plug-and-Play System The dynamics of a hot plug or hot unplug event in a USB system makes it very hard to determine when the system reaches the steady state. This is especially true for a system with multiple keyboards due to the fact that they can switch modes. This switching modes makes it appear to the system that different physical devices have been hot plugged. The steady state needs to be accurately determined prior to assigning the device role and cluster. See "A Means to Reliably Distinguish Multiple Identical Devices" and "Method to Reliably Identify and Support Multiple USB Device Clusters" disclosures. The algorithm described can be used to reliably determine whether or not the system has reached steady state.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 90% of the total text.

Page 1 of 2

A Means To Reliably Determine The Steady State Of A USB Plug-and-Play System

A Means To Reliably Determine The Steady State Of A USB

Plug-and-Play System

The dynamics of a hot plug or hot unplug event in a USB system makes it very hard to determine when the system reaches the steady state. This is especially true for a system with multiple keyboards due to the fact that they can switch modes. This switching modes makes it appear to the system that different physical devices have been hot plugged. The steady state needs to be accurately determined prior to assigning the device role and cluster. See "A Means to Reliably Distinguish Multiple Identical Devices" and "Method to Reliably Identify and Support Multiple USB Device Clusters" disclosures.

The algorithm described can be used to reliably determine whether or not the system has reached steady state.

A "snap shot" of the USB network topology is recorded for all devices along with their corresponding device mode, role, and cluster. This "snap shot" will be kept as a reference. When the system is notified of a device arrival or removal, this reference shot will be compared with the new one. This might be a new device physically connected or disconnected from the network or a keyboard that has switched modes. If they differ, the reference "snap shot" will

1

Page 2 of 2

be updated with the new one. Steady state is determined when there is no difference between the reference and the new "snap shot"
for a pre-determine...