Friday, September 30, 2016

Embedded System Glossary – D

Embedded System Terminology - D

Daisy Chain - A type of digital circuit in which components are connected in series (in a “chain-like” structure), and where signals pass through each of the components down through the entire chain. Components at the top of the chain essentially can impact (slow down, block, etc.) a signal for being received by components further down in the chain.
Datagram - What the networking data received and processed by the networking layer of the OSI model or corresponding layer in other networking models (the Internet layer in the TCP/IP model) is called.
Data Bus - A set of electrical signals connected to the processor and all of the memory and peripheral devices with which it communicates for the purpose of transferring data between them.
Data Acquisition System - System which acquires data, generally by digitizing analog channels and storing the data in digital form. These systems can be standalone or coupled to a computer and can acquire multiple channels of data.
Data Communications Equipment (DCE) - The device that the DTE wants to serially communicate with, such as an I/O device connected to the embedded board.
Data Terminal Equipment (DTE) - The initiator of a serial communication, such as a PC or embedded board.
Deadline - In a real-time system, the time at which a particular set of computations or data transfers must be completed. There are typically consequences associated with missing a deadline. If the deadline absolutely, positively must be met every time or else, it is called a hard deadline. Hard deadlines have dire consequences when missed. Other deadlines are said to be soft deadlines.
Deadlock - An undesired result related to the use of an operating system, in which a set of tasks are blocked, awaiting an event to unblock that is controlled by one of the tasks in the blocked set.
Debounce - Electrical contacts in mechanical pushbutton switches often make and break contact several times when the button is first pushed. A debouncing circuit removes the resulting ripple signal, and provides a clean transition at its output.
Debugger - A software tool used to test for, track down, and fix bugs.
Debug Monitor - A piece of embedded software that has been designed specifically for use as a debugging tool.
Decimal - A base-10 number system, meaning there are 10 symbols (0-9), used in a variety of combinations to represent data.
Decoder - A circuit or software that translates encoded data into the original format of the data.
Delay Line - An electrical component that delays the transmission of a signal.
Demodulation - Extracting data from a signal that was modified upon transmission to include a carrier signal and the added transmitted data signal.
Demultiplexor (Demux) - A circuit which connects one input to more than one output, where the value of the input determines which output is selected.
Device Driver - Software that directly interfaces with and controls hardware.
Device Programmer - A tool for programming EPROMs, PLDs, nonvolatile memories, and other electrically programmable devices.
Dhrystone - A benchmarking application which simulates generic systems programming applications on processors, used to derive the MIPS (Millions of Instructions per Second) value of a processor.
Die - The portion of an integrated circuit that is made of silicon, that can either be enclosed in some type of packaging or connected directly to a board.
Dielectric - An insulative layer of material found in some electrical components, such as capacitors.
Diode - A two-terminal semiconductor device that allows current flow in one direction, and blocks current which flows in the opposite direction.
Differentiator - A circuit that calculates a mathematical (calculus) derivative output based on a given input.
Digital - A signal that is expressed as some combination of one of two states, a “0” or “1”.
Digital Filter - A filter that's implemented digitally. A digital filter accepts digital inputs (typically samples read from an ADC) and produces digital outputs. The data is processed in firmware running on a digital signal processor.
Digital-to-Analog Converter (D/A Converter) - A hardware device that takes a set of bits, typically from a processor, as input and produces an analog signal proportional to the digital input as output.
Digital Signal Processor (DSP) - A type of processor that implements a datapath ISA, and is typically used for repeatedly performing fixed computations on different sets of data.
Digital Subscriber Line (DSL) - A broadband networking protocol that allows for the direct digital transmission of data over twisted pair wired (POTS) mediums.
Digital-to-Analog Converter (DAC) - A device that converts digital signals to analog signals.
Direct Current (DC) - Current that flows constantly in the same direction in a circuit. DC current is defined by two variables: polarity (the direction of the circuit) and magnitude (the amount of current).
Direct Memory Access (DMA) - A scheme in which data is exchanged between I/O and memory components on a board with minimal interference from and use of the master processor.
Disassembler - Software that reverse-compiles the code, meaning machine language is translated into assembly language.
Domain Name Service (DNS) - An OSI model session layer networking protocol that converts domain names into internet (network layer) addresses.
Down Counter - A counter that counts down, from its maximum value toward zero.
Dual Inline Memory Module (DIMM) - A type of packaging in which memory ICs can come in, specifically a mini-module (PCB) that can hold several ICs. A DIMM has protruding pins from 1 side (both on the front and back) of the module that connect into a main embedded motherboard, and where opposing pins (on the front and back of the DIMM) are each independent contacts.
Dual Inline Package (DIP) - A type of packaging that encloses a memory IC, made up of ceramic or plastic material, with pins protruding from two opposing sides of the package.
Dual Port Random Access Memory (DPRAM) - RAM that can connect to two buses allowing for two different components to access this memory simultaneously.
Dynamic Host Configuration Protocol (DHCP) - A networking layer networking protocol that provides a framework for passing configuration information to hosts on a TCP/IP-based network.
Dynamic Random Access Memory (DRAM) - RAM whose memory cells are circuits with capacitors that hold a charge in place (the charges or lack thereof reflecting the data).

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Related topics:
Embedded System Architecture   |   Embedded Hardware Architecture   |   Embedded Software Architecture   |   Embedded Software Definition   |   Embedded System Acronyms   |   Embedded System Symbols

List of topics: Embedded System

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