Terms and Abbreviations #

I’m listing here terms and abbreviations that were relevant for my research. Skipping some more mainstream ones like “audio device” and “Big Endian”.

ACK (packet) #

A packet that signals a positive handshake acknowledgement.

Active Device #

Device that is powered and not in suspend state.

Asynchronous Data #

Data transferred at irregular intervals with relaxed latency requirements.

Asynchronous RA #

The incoming and outgoing data rate of the RA process. The rates are in this case independent (notice async), meaning there is also no shared master clock.

Asynchronous SRC #

The incoming and outgoing sample rate of the SRC process.

Babble #

Unexpected bus activity that persists beyond a specified point in a (micro)frame.

Bit Stuffing #

Insertion of 0 bits into a data stream to cause electrical transition on the data wires.

b/s #

Bits/second

B/s #

Bytes/second

Buffer #

Storage used to compensate for a difference in data rates or time of occurrence of events, when transmitting data from on device to another.

Bulk Transfer #

One of the 4 USB transfer types. Non-periodic, large busty communication typically used for a transfer that can use any available bandwidth and can also be delayed until bandwith is available.

Bus Enumeration #

Detecting and identifying USB devices.

Capabilities #

Those attributes of a USB device that are administrated by the host.

Characteristics #

Those qualities of a USB device that are unchangeable; for example, the device class is a device characteristics.

Client #

Software resident on the host that interacts with the USB System Software to arrange data transfer between a function and the host. The client is often the data provider and consumer for transferred data.

Configuring Software #

Software resident on the host software that is responsible for configuring a USB device. This may be a system configurator or specific to the device.

Control Endpoint #

A pair of device endpoints with the same endpoint number that are used by a control pipe. Control endpoints transfer data in both directions and, therefore, use both endpoint directions of a device and endpoint number combination. Thus, each control endpoint consumes two endpoint addresses. See also Device Endpoint

Control Pipe #

Same as a message pipe.

Control Transfer #

One of the 4 USB transfer types. Control transfers support configuration/command/status type communications between client and function.

CRC (Cyclic Redundancy Check) #

A check performed on data to see if an error has occured in transmitting, reading or writing the data. The CRC is typically stored or transmitted with the checked data. This helps to determine if an error occured.

CTI #

Computer Telephony Integration

Default Address #

An address defined by the USB Spec and used by the USB device when it is first powered or reset. Default is 0x00.

Default pipe #

Message pipe created by the USB System Software to pass control and status information between the host and a USB device’s endpoint zero.

Device Address #

Seven-bit value representing the address of a device on USB. Default is 0x00. Addresses are uniquely assigned by USB System Software.

Device Endpoint #

A uniquely addressable portion of a USB device that is the source or sink of information in a communication flow between the host and device. See also Control Endpoint

Device Resources #

Resources provided by USB devices, such as buffer space and endpoints. See also Host Resources and Universal Serial Bus Resources.

Device Software #

Software responsible for using a USB device. May ir may bit also be responsible for configuring the device to use.

Downstream #

Direction of flow from the host or away from the host

Driver #

When reffering hardware - An I/O pad that drives an external load.
When referring software - A program responsible for interfacing to a hardware device (a device driver).

DWORD (Double Word) #

A data element that is two words. (e.g. four bytes or 32 bits when the word size is 2 bytes)

Dynamic Insertion And Removal #

The ability to attach and remove devices while the host is in operation.

End User #

The user of a host.

Endpoint #

Same as Device endpoint

Endpoint Address #

The combination of an endpoint number and an endpoint direction on a USB device. Each endpoint address supports data transfer in one direction. Basically there will be two addresses at least for a USB device. Each one address has then a bit that dictates the direction.

Endpoint Direction #

The direction of data transfer on the USB. This can be:

IN - transfer to the host
OUT - Transfers out from the host

Endpoint Number #

A four bit value between 0x0 and 0xF, inclusive, associated with an endpoint on a USB device.

EOF (End-of-(micro)Frame) #

Self explaining

EOP (End-of-Packet) #

Self explaining

Frame #

a 1 ms time based established on full/low -speed buses.

Frame Pattern #

A sequence of frames that exhibit a repeating pattern in the number of samples transmitted per frame.

Fs #

Sample rate

Full-duplex #

Simultaneously data transmission in both directions.

Function #

A USB device that provides a capability to the host (like mic, speakers).

Handshake Packet #

A packet that acknowledges or rejects a specific condition.

Host #

Host computer systm where the USB Host controller is installed.

Host Controller #

Host’s USB interface.

Host Controller (HCD) #

USB Software layer that abstracts the Host Controller Hardware.

Interrupt Request (IRQ) #

Signal to request attention from the host.

Interrupt Transfer #

One of the 4 USB transfer types. Small data, non-periodic, low-frequency and bounded-latency.

I/O Request Packet (IRP) #

An identifiable request by a software client to move data between itself and an endpoint of a device in appropriate direction.

Isochronous Data #

Stream of data whose timing is implied by its delivery rate.

Isochronous Device #

An entity with Isochronous endpoints.

Jitter #

Lack of synchronization.

Message Pipe #

Bi-directional pipe that transfers data using a request/data/status paradigm.

Microframe #

A 125 microseconds time base on high speed buses

NAK #

Rejecting handshake package

Object #

Host software or data structure representing a USB entity.

Packet #

A bundle of data organized in a group of transmission. Packets typically contain three elements:

Control information (source, destination and length)
Data to be transferred
Error detection and correction bits

Packet ID (PID) #

A field in packet that indicates the type of packet. By inference it indicates the format of the packet and the type of error detection.

Phase #

A token, data or handshake packet. A transaction has 3 phases.

Pipe #

Abstraction of the association between an endpoint of the device and the software on the host. A pipe has several attributes. So we have stream pipe’s and message pipes.

Polling #

Asking (multiple) devices if they have any data to trasmit.

Power on Reset (POR) #

Restoring a storage device, register or memory to a predetemrined state when power is applied.

Port #

Point of access to or from a system or circuit.

Rate Adaption (RA) #

Adapting the rate of a data stream with certain loss of quality.

Request #

A request made to a USB device contained within the data portion of a SETUP packet.