Introduction > Glossary

Binary file - A file that contains data or program instructions written in ASCII and extended ASCII characters.

ASCII - An acronym for American Standard Code for Information Interchange. ASCII files are plain, unformatted text files that are understood by virtually any computer. Windows Notepad and virtually any word processor can read and create ASCII files. ASCII files usually have the extension .TXT (e.g., README.TXT).

Bytes - A collection of eight bits that represent a character, letter or punctuation mark.

USB (Universal Serial Bus) - a "plug and play" interface between a computer and peripherals (like audio players, digital cameras, joysticks, keyboards, and printers), which lets you plug in a device without adding an adapter card or even restarting your PC.

Its speed makes it ideal for music and digital photo transfer. USB 1.1, the familiar USB standard of the last several years, supports a data transfer speed of 12 Mbps (megabits per second) — significantly faster than a serial connection. But new USB 2.0 standard is dramatically faster — 480 Mbps!

Today, most new computers (both IBM-compatible PCs and Macs) and many peripheral devices are equipped with USB; for example, USB support is integrated into Windows® 98, 98SE, 2000, 2000SE, ME and Windows XP, as well as Mac OS 8.6 and up.

All new computers equipped by high-speed USB 2.0 interface.

ACK - Handshake packet indicating a positive acknowledgement between devices or a host and device on the USB bus.

Active device - A device that is not in the suspended state and is powered on.

Asynchronous data - data that is sent across the USB bus without regard to timing requirements, the opposite to isochronous.

Babble - Persistent data on the bus that is not expected by any device or host.

Bandwidth - The amount of data that can be transmitted over the bus in a given amount of time. Usually expressed in bits per second (bps).

Bit - A single element within the computer (or on the bus) that is either a 1 or 0. There are eight bits in a byte of data.

Buffer - Temporary storage are used by the computer (or USB device) to put data when it cannot be immediately used.

Bulk transfer - Movement of large blocks of data across the USB bus that is not time critical (i.e. a large asynchronous transfer).

Bus enumeration - The process of detecting and identifying USB devices.

Byte capabilities - The functional parameters of a device that can be controlled by the host software.

Characteristics - Functionality within the USB device that is not changeable by the host software.

Client - The software on the host that is the highest level user of the USB device.

Control pipe - A pipe used to send configuration and control information from the host computer to a device on the USB bus.

Control transfer - A transfer over the control pipe from the host computer to a device on the USB to provide configuration and control information to a USB device.

CRC - Cyclic redundancy check; used to detect errors in the transmission of data across the bus. The CRC is transmitted along with the data packets for comparison with a CRC calculated by the receiving device.

Default address - The address that a USB device responds to before the host software sets the desired address on the device.

Default pipe - A message pipe created by the host system software to exchange control and status information with the USB device's endpoint zero.

Device - A logical or physical entity that performs a function. The actual entity described depends on the context of the reference. Usually referring to the device attached to the USB bus.

Device address - The address of a device on the USB bus. The address is the default address when the USB device s first powered or reset. Hubs and functions are assigned a unique device address by the USB host software.

Device endpoint - A uniquely identifiable portion of a USB device that is the source or sink of information in a communication flow between the host and device.

Downstream - The direction of data flow from the host.

Driver - A program responsible for interfacing to a hardware device, i.e. device driver.

Interrupt transfer - USB Interrupt data is typically small packets of data that are used by the USB device to send status information to the computer.

Isochronous transfer - one of four USB transfer types. Isochronous transfers are used when working with isochronous data. Isochronous transfers provide periodic, continuous communication between hosts and device.

Upstream - The direction of data flow to the host.