USB is a wired high-speed serial bus standard used for data transfer between devices. It uses a star topology and supports up to 127 devices connected to a host controller. USB transfers data in packets containing header, payload, and status information. It supports various transfer types including control, isochronous, bulk, and interrupt. USB comes in various speeds defined by its specifications and uses standardized connectors to connect devices to hosts.

1. USB
BY
SUKESH SHETTY

2. Universal serial bus
 Wired high speed serial bus for data communication
 follows star topology
 Supports connection up to 127
 USB is a n/w of attachments connected to host which
comes in 2 types namely “functions”& “hubs”
 USB host contains host controller responsible for
controlling data communication
 Different std. to implement USB host control
interface are open host control interface (OHCI) &
Universal host control interface(UHCI).

6. Transmits data in packet form having standard
format
Each USB data transfer consists of
- Token packet (header defining what it wants
to follow)
- Optional data packet (contains the payload)
- Status packet (used to acknowledge
communication & provides a mean for error
correction)
USB cable connects peripheral device & master
device

7. USB std uses two types of connector for
connecting peripheral device & host device
- Type A
- Type B
Both these connectors have 4 pins for
communication
Each USB device has Product ID (PID) &
Vendor ID (VID)
PID & VID are essential for loading the
drivers corresponding to a USB device

10. • USB supports 4 types of data transfers
• 1. Control
2. Isochronous
3. Bulk
4. Interrupt
• Control transfers exchange configuration, setup and command information
between the device and the host. The host can also send commands or
query parameters with control packets.
• Isochronous transfer is used by time critical, streaming device such as
speakers and video cameras. It is time sensitive information so, within
limitations, it has guaranteed access to the USB bus. Data streams between
the device and the host in real-time, and so there will not be any error
correction.
• Bulk transfer is used by device like printers & scanners, which receives
data in one big packet. Here the timely delivery is not critical. Bulk
transfers are fillers, claiming unused USB bandwidth when nothing more
important is going on. The error correction protects these packets.
• Interrupt transfers is used by peripherals exchanging small amounts of
data that need immediate attention. It is used by devices to request
servicing from the PC/host. Devices like a mouse or a keyboard comes in
this category. Error checking validates the data.

11. USB supports 4 different rates
- Low speed (1.5Mbps)
- Full speed (12Mbps)
- High speed (480Mbps)
- Super speed (4.8Gbps)
Low speed & Full speed are defined by USB1.0
High speed is defined by USB 2.0
Super speed is defined by USB 3.0

12. • USB Features
• The Universal Serial Bus has the following features:
• The computer acts as the host.
• Up to 127 devices can connect to the host, either directly or by way of USB hubs.
• Individual USB cables can run as long as 5 meters; with hubs, devices can be up to 30 meters
(six cables' worth) away from the host.
• With USB 2.0,the bus has a maximum data rate of 480 megabits per second (10 times the
speed of USB 1.0).
• A USB 2.0 cable has two wires for power (+5 volts and ground) and a twisted pair of wires to
carry the data. The USB 3.0 standard adds four more wires for data transmission. While USB
2.0 can only send data in one direction at a time (downstream or upstream), USB 3.0 can
transmit data in both directions simultaneously.
• On the power wires, the computer can supply up to 500 milliamps of power at 5 volts. A USB
3.0 cable can supply up to 900 milliamps of power.
• Low-power devices (such as mice) can draw their power directly from the bus. High-power
devices (such as printers) have their own power supplies and draw minimal power from the
bus. Hubs can have their own power supplies to provide power to devices connected to the
hub.
• USB devices are hot-swappable, meaning you can plug them into the bus and unplug them
any time. A USB 3.0 cable is compatible with USB 2.0 ports -- you won't get the same data
transfer speed as with a USB 3.0 port but data and power will still transfer through the cable.
• Many USB devices can be put to sleep by the host computer when the computer enters a
power-saving mode.
• The devices connected to a USB port rely on the cable to carry power and data.

13. THANK YOU…