Token packets - universal serial bus, Computer Engineering

Token packets in universal serial bus - computer architecture:

Token packets consist of a PID byte followed by two payload bytes: a 5-bit CRC and 11 bits of address. Tokens are just sent by the host, never by a device.

IN and OUT tokens have a 4-bit device number (for multifunction devices) and 7-bit function number and command the components to transmit DATA x packets, or retain the following DATA x packets, respectively.

An IN token expects a response from a device. The response can be a STALL or NAK response, or can be a DATA x frame response. In the afterward case, the host issues an ACK handshake if it is appropriate.

An OUT token is followed immediately by a DATA x frame. The component responds with, STALL, NYET, ACK or NAK as appropriate. SETUP operates mostly like an OUT token, but it is used for initial component setup. It is followed by an 8-byte.DATA0 frame with a standardized format.

In every millisecond (12000 full-speed bit times), the USB host transmits a special SOF (start of frame) token which is containing an 11-bit incrementing frame number in place of a component address. It is used to synchronize isochronous data flows. High-speed USB 2.0 devices retain 7 additional duplicate SOF tokens per frame, each introducing a 125 µs "micro frame" (60000 high-speed bit times each).

USB 2.0 added a PING token, which asks components if it is ready to retain an OUT/DATA packet pair. The components respond with NAK, ACK or STALL, as appropriate. It avoids the requirement to send the DATA packet if the components know that it will just respond with NAK.

USB 2.0 also added a larger 3-byte SPLIT token having a, 12 bits of control flags, 7-bit hub number and a 5-bit CRC. It is used to perform split transactions. Or else tie up the high-speed USB bus sending data to a slower USB device, the closest high-speed capable hub retain a SPLIT token followed by 1 or 2 USB packets at high speed, performs the data transfer at low or full speed, and provides the response at high speed when prompted by a second SPLIT token. The details are completed; see the USB specification.

Posted Date: 10/13/2012 7:48:47 AM | Location : United States







Related Discussions:- Token packets - universal serial bus, Assignment Help, Ask Question on Token packets - universal serial bus, Get Answer, Expert's Help, Token packets - universal serial bus Discussions

Write discussion on Token packets - universal serial bus
Your posts are moderated
Related Questions
c programming code for pebble merchant

A NULL pointer is a pointer of any type whose value is zero. A void pointer is a pointer to an object of an unknown type, and is guaranteed to have sufficient bits to hold a pointe

Application and Function Areas - artificial intelligence: Individual applications and function often drive "AI" research much more than the long term relative field described

Q. State any three properties of the neutrons. (i) A Neutrons are the constituent particles of all nuclei except hydrogen. (ii) As they are neutral particles they aren't de

Question: (a) Briefly explain how the functionality of the WWW has been enhanced, after its birth at CERN site. Use examples to illustrate your answer. (b) Many modern com

Define Input-Output Interface. I/O interface gives a method for transferring information among internal storage and external I/O devices

Q. Write a program to implement OR, NOR, AND and NAND gates using and without using Bit wise operator. The menu should be as follows: I. Using Bit Wise operator II. Withou


Write a program to read in a positive integer and check whether it is prime or not? /* Program to check whether a given number is prime or not*/] # include # include

Explain an exceptional handling in java with the help of suitable example. Java exception handling is managed through five keywords: catch, try, throw, finally and throws. Th