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Method for the insertion of debug port device traffic into a universal serial bus host-controller transaction schedule

IP.com Disclosure Number: IPCOM000009108D
Publication Date: 2002-Aug-07
Document File: 3 page(s) / 56K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for the insertion of debug port device traffic into a universal serial bus (USB) host-controller transaction schedule. Benefits include improved functionality.

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Method for the insertion of debug port device traffic into a universal serial bus host-controller transaction schedule

Disclosed is a method for the insertion of debug port device traffic into a universal serial bus (USB) host-controller transaction schedule. Benefits include improved functionality.

Background

      A debug port device is a console used by operating-system (OS) programmers to monitor and/or modify internal memory by accessing data by way of a hardware interface on a personal computer (PC). Conventionally, the interface is the RS-232 serial interface.

      The conventional serial interface [DA1] is being replaced by a universal serial bus (USB) implementation. In the future, a requirement may exist for the debug console to communicate with the OS via USB hardware.

      A USB host controller comprised of hardware and software is, ideally, constantly busy with packet-based traffic to USB devices. USB devices can be categorized into two types, asynchronous and periodic. A periodic device requires data to be delivered at a particular time and at a particular rate. An asynchronous device requires data to be error-free.

      A USB transaction consists of one or more serial packets that are signaled on a USB wire.

      A microframe is a concept only applicable to the high-speed implementation of USB (USB 2.0). A microframe is a period of time for which the beginning is marked by the transmission of a start of frame (SOF) packet. SOF packets are sent at near-constant intervals so that devices have a usable concept of timing. The amount of time that spans between two SOF packets is typically 125 microseconds. If any devices are using the USB physical media when it is time for the SOF packet to be transmitted, they are disabled by the host controller.

      Due to the time-sensitive nature of periodic data, transaction...