Token packets - universal serial bus, Computer Engineering

Assignment Help:

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.


Related Discussions:- Token packets - universal serial bus

Typewriters information distribution, TYPEWRITERS : Typewriter is the most...

TYPEWRITERS : Typewriter is the most common machine used in almost all offices. Typewritten letters are attractive in appearance as compared to handwritten ones. The same matter c

Catch output from child tasks, Q. Catch output from child tasks? ...

Q. Catch output from child tasks? int pvm_catchout( FILE *ff ) Catch output from child tasks. ff is file descriptor on which we write collected output. The defau

Reprographic technologies, Reprography: Reprography, as a term, has ga...

Reprography: Reprography, as a term, has gained international recognition in 1963. It includes "photocopying , microcopying, duplicating and in-plant printing and is character

When a network uses a star topology, A Network uses a star topology if? ...

A Network uses a star topology if? A Network utilizes a star topology if all computers attach to a single central point.

Graphic symbol of S-R flip-flop, Q. Graphic symbol of S-R flip-flop? R...

Q. Graphic symbol of S-R flip-flop? R-S Flip flop - Graphic symbol of S-R flip-flop is displayed in Fig below. It has 3 inputs S (set), R (reset) and C (for clock). Q(t+1) is

NETWORK ADMIN, Discuss the risks of having a single root user and how more ...

Discuss the risks of having a single root user and how more limited management abilities can be given to others users on Linux/UNIX systems.uestion #Minimum 100 words accepted#

Grapgh, representation of the adjacency matrix and adjacency list

representation of the adjacency matrix and adjacency list

Computer Graphics , What do you mean by ‘Bresenham’s him Algorithm?

What do you mean by ‘Bresenham’s him Algorithm?

Optimum solution based on constraint problems, Optimum solution based on co...

Optimum solution based on constraint problems: Whether depending on what solver you are using so there constraints are often expressed as relationships between variables as e.

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd