The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 01, 2003
Filed:
Jan. 28, 2000
David R. Wooten, Spring, TX (US);
Compaq Information Technologies Group, L.P., Houston, TX (US);
Abstract
A computer system has a USB bus to which one or more USB-compatible devices can connect. One or more of the USB devices has an electrical interface that includes two transmitters and, if desired, a receiver for bidirectional data transmission. The transmitters preferably are dual output, differential transmitters. The transmitters include a slower transmitter and a faster transmitter. The faster transmitter can transmit data at a rate that is faster than the slower transmitter. The electrical interface also includes an electrical termination device that is disposed between the output terminals of the two transmitters. The termination device preferably comprises a pair of multi-purpose termination resistors that can provide serial termination or parallel termination depending whether the fast or slow transmitter is used. When transmitting using the slower transmitter, the receiving USB device disables all of its transmitters and the transmitting USB device disables the output of the faster transmitter by deasserting an output enable (OE) signal to the faster transmitter. The termination device provides serial termination and the data from the slower transmitter passes through the termination device. When transmitting using the faster transmitter, both receiving and transmitting USB devices assert single ended zero (SE ) signals to their slower transmitters which forces both of the slower transmitters' output signals to a low impedance state. In this latter transmission mode, the termination device provides parallel termination, effectively functioning as a “pull-down” terminator. With parallel termination, echoes effectively are reduced or eliminated and faster data rates are thereby attainable than are generally possible with serially-terminated transmission lines.