Intel PXA27 Series Design Manual page 280

Glossary
D-cache. Data cache
DECT. The Digital European Cordless Telecommunications standard
Default Address. An address defined by the USB Specification and used by a USB device when it is first powered
or reset. The default address is 00H.
Default Pipe. The 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. A logical or physical entity that performs a function. The actual entity described depends on the context of
the reference. At the lowest level, "device" may refer to a single hardware component, as in a memory device. At a
higher level, it may refer to a collection of hardware components that perform a particular function, such as a USB
interface device. At an even higher level, device may refer to the function performed by an entity attached to the
USB; for example, a data/FAX modem device. Devices may be physical, electrical, addressable, and logical. When
used as a non-specific reference, a USB device is either a hub or a function.
Device Address. A seven-bit value representing the address of a device on the USB. The device address is the
default address (00H) when the USB device is first powered or the device is reset. Devices are assigned a unique
device address by the 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 Endpoint Address.
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 that is responsible for using a USB device. This software may or may not also be
responsible for configuring the device for use.
DMA. Direct Memory Access
Downstream. The direction of data flow from the host or away from the host. A downstream port is the port on a
hub electrically farthest from the host that generates downstream data traffic from the hub. Downstream ports
receive upstream data traffic.
DQPSK. Differential Quadrature Phase Shift Keying a modulation technique used in TDMA.
Driver. When referring to hardware, an I/O pad that drives an external load. When referring to software, a program
responsible for interfacing to a hardware device, that is, a device driver.
DSP. Digital Signal Processing
Data Set Ready (DSR). When low, indicates the modem or data set is ready to send signal and establish a
communications link with a UART.
DSTN (Double-layer Supertwist Nematic). A passive LCD panel that uses two display layers to counteract the
color shifting that occurs with conventional supertwist displays. See STN.
Data Terminal Ready (DTR). When low, signals the modem or data set that the UART is ready to communicate.
Dual band mobile phone. A phone that supports both analog and digital technologies by picking up analog signals
when digital signals fade. Most mobile phones are not dual-band.
Digital Volt Meter. This equipment is used for measuring voltage across a series resistor, preferable for high
current power supplies. For low power supplies, the voltage drop is too small for detection by the DVM.
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Glossary-4 Intel PXA27x Processor Family Design Guide