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# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Not including IC packages.


Term Meaning Comments
2-wire Generally means I2C* (Term used by manufacturers without a licence from Philips)
3S Tri-state Output can be put in high-impedance mode


Term Meaning Comments
ACIA Asynchronous Communications Interface Adapter Also called UART. More
ACPI Advanced Configuration and Power Interface PC term
ACR Advanced Communications Riser, probably similar to an AMR* PC term
A/D Analog to Digital
ADC* Analog to Digital Converter
ADMA Advanced DMA* controller Siemens
ADPCM Adaptive Differential Pulse Code Modulation Both the sender and the receiver predict what the next sample will be based on the fact that the human voice and simple modem* signals never contain two frequencies at once and then instead of sending the complete 8 bits PCM* code only the difference is send in 4 bits.
ADTV Advanced Definition TV
AGC Auto Gain Control Adjusts input audio volume automatically. Not easy to do. May severely distort recordings. Beware!
AGP* Accelerated Graphics Port This port was added after the PCI* bus proved to be to slow for graphics. Disadvantage: Only one AGP* slot per motherboard so multiple displays becomes more difficult. 2002: Even low-cost ($90) modern AGP* video cards can handle multiple displays now, although the second one is usually configured on the card to be a TV.
ALI ATM Line Interface TranSwitch
AM Amplitude Modulation The amplitude variation of a wave carries a slower wave.
AMDM ATM Multiplexer/DeMultiplexer (QSI)
Amp Amplifier Chipwise usually an OPerational AMPlifier (OpAmp*). There is also a company called AMP. They mainly make (good!) connectors.
AMR* Audio Modem* Riser. This is a small card you prick into the motherboard and it contains enough (dependend on country) hardware, so the CPU* can emulate a (soft-) modem* with it. PC term
AND The logical AND* function. The output is high if and only if all inputs are high.
AOI And-Or-Invert First a couple of AND-ports, whose outputs go into a single NOR* port. The last inversion is probably because NOR* ports are faster then OR*'s and because ports with inverted outputs offer more possibilities.
APM Advanced Power Managament PC term
ARCOFI Audio Ringing COdec* FIlter Siemens
ASLAC Advanced Subscriber Line Audio processing interface AMD
ASLIC Advanced Subscriber Line Interface AMD
Async Asynchronous Not clocked, so just a bunch of logic ports one after another.
atto 10**-18


Term Meaning Comments
Baud Unit for baudrate* (next entry).
Baudrate Signal level changes per second. Often confused with BPS*. Named after mister Baudot. In early modems the baudrate* was equal to the BPS*, hence the confusion.
BCP Biphase Communications Processor NS
BinHex The Apple way to code binary files using visible ASCII-only to fascillitate sending the data over pure-ASCII (or unknown) networks. The UNIX variation is UUEncode. Usually the datastream is chopped in parts of six bits and ' ' is added. This has the extra advantage that only upper case characters are used. Old computers couldn't handle lower case letters. More.
BIOS Basic Input Output System, the (EEP)ROM that handles how a PC starts up PC Term
BPS Bits Per Second This is relevant for serial connections. Beware that the nominal and actual bitrate may differ depending on the reliability of the medium. Once a medium has a certain reliability you can enhance it's reliability to whatever you like by sacrificing speed.


Term Meaning Comments
CAD Computer Aided Design Using a computer to design products. For PCB* CAD* programs see local.
CAM Computer Aided Manufacturing It's the next step after CAD*. Together they are often called CAD*/CAM*. See also the next entry.
CAM* Content Addressable Memory The memory is not addressed according to it's linear address but by it's content, usally some sort of tag to gain access to the real data. This kind of memory was originally often used to implement MMU*'s. Currently two-way associative look aside buffers are more common, because they can work faster (less drain on the address lines). This means that the part of the address lines that are used for associative purposes becomes smaller and the deterministic part bigger. With a two way caching mechanism however you can get into serious caching problems when copying arrays etc. For example when adding the elements of two screen image arrays and putting it in the video RAM*.
CAN Controller Area Network Type of network. see local
CC C compiler Compiler for the language C
CCD Charge Coupled Device Kind of DRAM*, that can sense light intensities. local.
CDB Cell Delineation Block device TranSwitch
CDR Clock and Data Recovery TranSwitch
CISC Complex Instruction Set Computing As opposed to RISC. CISC* was the classic way of designing processor instruction set. It was based on the misapprehention of the hardware designers that the programmers were still programming in Assembler and wanted powerful addressing modes. Compilers don't like complex instructions however.
CMOS Complementary Metal Oxide Semiconductor The 4xxx range was a very popular range of early glue semiconductors. It's already very old (1980 or earlier), both on those days static was a problem with CMOS*. Later CMOS* became the standard in the industry because of it's low energy consumption and even modern TTL* (since about 1985?) is done in CMOS* (HCT*). See local.
CNR Communication and Networking Riser, probably similar to AMR* PC term
Codec COder and DECoder This is a combined ADC* and DAC* for telecom purposes. The digital format is usually A-law or µ-law PCM*. More.
COFF* Meant to be a universal format for binary files. Every computer type uses it's own variation however.
COFI COdec* FIlter
COFISLIC COdec* FIlter and Subscriber Line Interface Circuit AMD
CompactPCI* Passive backplane specification for (industrial) PCI*.
CPU* Central Processing Unit This is called MPU* on these pages, because we're only thinking in terms of chips here. CPU*'s were once implemented as many-IC PCB*'s in mainframes and mini computers and therefore single chip CPU*'s were called microprocessors or MPU*'s. Nowadays all CPU*'s are single chip and the makers of big computers try to put as many of them in a single computer to offer as much power as possible.
CRIMM Continuity RIMM PC term?
CRT Cathode Ray Tube This is the basic part of a video monitor that actually shows the images. A television set has additional circuitry to decode and select one out of several broadcasting channels and to handle audio, teletext and in future even much more.
CTC Counter Timer Circuit Counters and timers are basically the same because timers just count time ticks. However since we see time as an absolute continuum, in our nativity we tend to make a difference.


Term Meaning Comments
D/A Digital to Analog
DAA* Data Access Arrangement
DAC* Digital to Analog Converter MPU*'s and MCU*'s 'think' digitally so to convert these 'thoughts' to the real world we need to convert this, usually parallel binary, data to an analogue voltage or current. The simplest solution is using a resistor network costing only a few dimes. Another cheap solution is generating a square wave with a certain high-low ratio (duty cycle) and feeding that via a resistor into a capacitor which will then average it out. There are also much more sophisticated solutions. The company 'Analog' got big specializing on this.
DART Dual* Asynchronous Receiver Transmitter Two UART's
DCF-77* Time info transmitter in Mainflingen, Germany. Only usable in a circular area around the transmitter in Europe. local.
DCPAT Dual* CEPT Primary Access Transceiver AT&T*
DD Double density Floppy disk type. DD* uses a more advanced bit coding than Single Density (SD*). SD* and DD* floppies are the same. See also High Density (HD*).
DDR Double Data Rate. DRAM* with this feature can be read on both flanks of the clock signal, doubling the amount of data they can provide with the same clock rate. Currently (2002) it's mainly a technology used on video cards, I think.
DDS Direct Digital Synthesis The IC*'s AD7008 and AD9850 from Analog Devices are often used as computer controlled signal generators in highend RF applications. The integrated circuits generate a high quality sinewave with nearly constant amplitude between about 0,01 Hz and 65 MHz. Frequency and phase angle of the output signal are being varied by serial input data. The ideal circuit for HAM radio ;-)
Demux Demultiplexer
DIMM Dual* Inline Memory Module modern type of DRAM* memory on a small plug-in board, see also SIMM. Early PC motherboards used sockets for DRAM* chips, but it was very hard to predict which memory chips would be cheap once the board was finished. It's easier to put SIMM/DIMM sockets on the board and let others take care of the issue, which chips to put on them.
DMA Direct memory access See next entry
DMAC Direct memory access controller This is a separate, very simple but fast co-processor (consisting mainly of counters) that is allowed to handle the address and data lines of the system (after being instructed to do so by the main processor). It will either 'steal' single cycles on the bus or do 'burst' accesses, mainly to do I/O. The usefulness of DMA* during a certain era depends heavily on the difference in speed between the processor and the system and it's interrupt overhead. It also depends on if the peripheral will need to be serviced regurarly with single bytes or small blocks or that it can buffer data itself and do a burst just now and then. With the current trend to put more and more memory and intelligence in the peripherals and CPU*'s getting faster and faster DMA* is gradually getting more and more obsolete. Even modern UART's already have an internal 64 bytes buffer so the CPU* can handle them and DMA* is not needed.
DMI Direct Management Interface PC term
DPST Double Pole, Single Throw Type of switch
DRAM* Dynamic Random Access Memory See DRAM*
DRM Dual* Rentention Mechanism PC term
DS Double sided Floppy disk term
DSP* Digital Signal Processor See DSP*.
DSR Dynamic Shift Register Also RS-232 term: Data Set Ready. DTR means 'Data Terminal Ready'. 'Set' means 'modem*' since RS-232 mainly dealed with the terminal-modem connection situation. A PC was traditionally seen by IBM as a terminal and not as a real computer...
DTMF* Dual* Tone Multi-Frequency This is the system to code special information over a traditional analogue telephone line. Normally a single person only uthers one frequency at a time. By sending two frequencies at the same time for a certain time (about 0.1 s) it's possible to make quite sure not to get these tones confused with human speech. The frequencies are choosen such that they have no harmonics in common. For a receiver, check out the Mitel MT8870 (second sourced by Samsung). For a sender check out the Philips I2C* part PCD3311*, PCD3311A* or PCD3312*.
Dual Containing 2 equal devices
DUART Dual* Universal Asynchronous Receiver Transmitter Device with two UART's


Term Meaning Comments
ECL Emitter Coupled Logic Is very fast and expensive
ECP Extended Capabilities Port PC term
ECC Error Checking and Correcting. Parity can only detect errors, but ECC can also repair it, assuming that there are only single bit errors now and then. It requires only 30% or such more bits to be transmitted. Check a good book about datacommunication about this subject...
EDO-RAM Extra (Extended?) Data Output RAM* See also DRAM*
EDTV Enhanced Definition TV
EEPROM* Electrically Erasable Programmable Read Only Memory
EMC Electro Magnetic Compatibility
EPP Enhanced Parallel Port Enhancement of the parallel printer port of the PC. The first port only had 8 data bits out and 4 control lines in and a handshake line, I think (see Centronix port). Later enhancements include 8 bits in and out and bididrectional features etc. Look in this Chipdir's ABC under the P for more info.
EPROM Erasable Programmable Read Only Memory
ESCD Extended System Configuration Data PC term
ESD Electro Static Discharge
Exa 10**18 or for computers 1024**6


Term Meaning Comments
FAQ* Frequently Asked Questions
FCODE Forth Code Processor independent language to write device drivers for the PCI-BUS. local.
FDC Floppy Disc Controller This is the chip (or formally the board) that controles the floppy disc drive. Basically there are two families: The 1771 family by Western Design/Digital Corporation (?) and the 765 family by NEC (same as 8272 by Intel, but who did really design it?).
FDD Floppy Disk Device This is a floppy disk drive
femto 10**-15
FET Field Effect Transistor. This is a voltage driven transistor. (The much more popular PNP and NPN transistors are current driven.)
FFT Fast Fourier Transformation This is a method to transform data from the time domain (that we normally live in) to the frequency domain (which is only interesting for freaks who want to study trends in signals). Of course those freaks make a good living of off their knowledge because examining trends can be big business. Simple consumers like us may notice FFT* in our hifi sets when it has a display which shows the energy in different frequency ranges.
FIFO First In First Out Like in a queue in the post office. The alternative is a stack or LIFO (Last In First Out).
FM Frequency Modulation A slower wave is carried by the small frequency variations of a carrier wave. The predecessor was AM* which carried it's child wave using variations in amplitude. This however was much more prone to distortions, because the amplitude of a signal suffers from all kinds of reflections etc. FM* uses more bandwidth in turn however.
FPAA Field Programmable Analog Array Enables building fast analog circuits. Motorola seems to have left this field now...
FPDRAM Fast Page DRAM*. Outdated by EDO and SDRAM* etc.
FPGA* Field Programmable Gate Array This is a 'cheap' way to design your own chips. All the components are already on the chip, but 'in the field' you program them to make the right connections between the components. Cheap is not really true for large amounts since the chip will use a lot of energy for the components that you're not really using. These components are also expensive because they carry a lot of unused silicon around. They may also be slow. Startup time may be hindered by the fact that their functionality needs to be loaded from a serial ROM. The software needed to achieve the functionality may also be expensive and getting used to the software may also take time. However once the design is ready and tested there may be an easy path to having the design being mass produced in a real ASIC. Xilinx became big making these FPGA*'s.
FSB Front Side Bus
FS-PAL Field Sequential Phase Alternation Line
FYI For Your Information


Term Meaning Comments
giga 10**9 or for computers 1024**3
GLU General Logic Unit
GLUE Generally 7400-series chips to glue (connect) VLSI-chips together This is a popular/meta term, so use with caution.
Gnd Ground voltage level Normally referred to as 0V. However be aware that there may be several Gnd* levels in a system. There is the board ground per board, the chassis ground and when interconnecting systems there may occure ground loops that can pick up magnetic fields etc.


Term Meaning Comments
HCMOS High-speed Complementary Metal Oxide Semiconductor
HCT High-speed CMOS* TTL* compatible
HD High density Floppy disk type. HD* uses the same coding as DD*, but just reads and writes twice as fast.
HDD Hard Disk Device/Drive PC term
HDTV High Definition TV A TV with a higher resolution on screen.
Hex Containing 6 equal devices Also: Hexadecimal (16) base notation for numbers.
HP Horse Power On switches. A switch must be rated for as many horsepower as the motor it can switch on and off.
HPC High Performance microController Old term used by NS. Look under MCU*. Can also mean: Hand-held Personal Computer, High Performance Computing or High Pressure Compressor
HQX File name extension of BinHex* files See BinHex*.
HV-SLIC High Voltage Subscriber Line Interface Circuit


Term Meaning Comments
I2C* (=IIC) Intra Integrated circuit (-bus) Philips
IC Integrated Circuit It's usually called chip on these pages
ICE* In-Circuit Emulator Expensive apparatus to simulate a processor. Also the name of a company.
IDE* Integrated Dual* channel Enhanced see IDE*
IEC* International Electrotechnical Commission (see IEC*)
IO Input and Output
I/O Input and Output
IOAPIC Input Output Advanced Programmable Interrupt Controller PC term
I-PAL Improved PAL*
IRQ Interrupt ReQuest
ISA-bus Industry Standard Architecture Bus in the IBM-PC. Later came EISA, VLB (VESA* Local Bus), PCI* and USB.


Term Meaning Comments
JEDEC* Joint Electronics Design Engineering Council
JTAG Joint Test Action Group of IEEE Defining test interfaces for integrated circuits, for example a boundary scan interface for digital ICs in the IEEE 1149.1 standard. To my knowledge other interfaces - e.g. for analog chips - are in development and will be published as IEEE 1149.2, 1149.3 and so forth.


Term Meaning Comments
kilo 2**3 = 1000 or for computers 1024


Term Meaning Comments
LAN Local Area Network PC term
LBA Logical Block Addressing Way of adressing IDE* drives
LCAS Line Card Access Switch AT&T*
LED Light Emitting Diode
LS Low-power Schottky Kind of TTL*. Succeeded by HCT*.
LSI Large Scale Integration. Also the name of a company.
LV-SLIC Low Voltage Subscriber Line Interface Circuit


Term Meaning Comments
M13 DS1/DS3 Multiplexer TranSwitch
M13E DS1/DS3 Multiplexer Extended features TranSwitch
MAC Multiplexed Analogue Components
mega 10**6 = 1000*1000 For computers 2**20=1024*1024 and for harddisks sometimes even 1000*1024
MEMS MicroElectro Mechanical Systems, see for example:
MFAST Mwave Folded Array Signal Transform (IBM)
MFLOPS Mega* Floating Point Instructions Per Second
MHz Mega* HertZ 1000,000 times per second
micro 10**-6
MIDI* Musical Instrument Digital Interface
milli 10**-3
MMU Memory Management Unit
Modem* Modulator/demodulator (follow the link).
MOS Metal Oxide Semiconductor As in CMOS*
MOSFET Metal Oxide Semiconductor Field Effect Transistor (FET*)
MPT Memory Protocol Translator PC term
MPU* Micro* Processor Unit (=single chip CPU*)
MSI Medium Scale Integration
MTH Memory Translator Hub PC term
MUART Multifunctions Universal Asynchronous Receiver Transmitter
Mudem Multiplexer and Demultiplexer Not an official term
Mux Multiplexer


Term Meaning Comments
NAND Not-AND A NOT-operation after an AND-operation
nano 10**-9
NIC Network Interface Card PC term
NIU Network Interface Unit Dallas
NMOS NPN-transistors-only Metal Oxide Semiconductor
NOR Not-OR A NOT-operation after an OR-operation
NOT The output is high if the input is low and low if the input is high
NTSC National Television System Committee or 'Never The Same Color' ;-) American color television standard
NV Non volatile (Keeps it's contents without power-connection)
NVRAM Non volatile RAM* (Keeps it's contents without power-connection)
NXOR Not-XOR (The result is a NOT-operation after an XOR-operation)


Term Meaning Comments
OC Open collector Needs pull-up resistor
Octal Containing 8 equal devices Same as Octuple
OEM Original Equipment Manufacturer
OI Opto Isolator
OpAmp Operational Amplifier
OR The output is high if at least one of it's inputs is high.
OS* Operating System
OTP One Time Programmable
OTPROM One Time Programmable Read Only Memory


Term Meaning Comments
PAC Primary Access framer/Controller AT&T*
PCI* AGP* Controller PC term
PAL Programmable Array Logic (=chip) or Phase Alternation Line (=European color television standard)
PBSRAM Pipeline Burst SRAM* Used as cache
PCB* Printed Circuit Board
PCI* Peripheral Component Interconnect PC and Macintosh bus
PCM Pulse Code Modulation
PEEL Programmable Electrically Eraseable Logic See ICT*.
Peta 10**15 or for computers 1024**5
PIA Parallel Interface Adapter
PIC Peripheral Interrupt Controller (Intel) or Peripheral Interface Controller (MicroChip)
pico 10**-12
PIO Parallel Input Output Usually called PIA*
PIPO Parallel in parallel out
PISO Parallel in serial out
PLA Programmable Logic Array
PLL Phase Locked Loop
PMOS P-type Metal Oxide Semiconductor
POST Power-On Self Test PC term
PROM Programmable Read Only Memory
PSRAM Pseudo SRAM* which is basically the same as dynamic RAM* with on-chip refresh circuitry. Same stuff from Sharp is called "SmartCombo SRAM*". The trade-off is: Lower cost, but slightly higher current consumption in low power mode. Stig Nielsen. Intel


Term Meaning Comments
QDS1F Quad* DS1 Framer TranSwitch
Quad Containing 4 equal devices Short for Quadruple
Quint Containing 5 equal devices Short for Quintuple


Term Meaning Comments
RAM* Random Access Memory
Ref Reference Voltage (Used for A/D* Converters). Can also mean refresh rate in DRAM*.
RIMM Rambus In-line Memory Module kind of SIMM, but using Rambus type DRAM* chips
RISC* Reduced Instruction Set Computing. local, local.
ROM Read Only Memory
RS232 The norm for serial transmission to terminals, modems and printers
RTOS Real Time Operating System Normal operating systems use as long as it takes to complete their tasks, but real time operating systems are designed such that the makers can quarantee a certain maximum response time for all kinds of events like interrupts.


Term Meaning Comments
SAR Successive Approximation Register Part of an ADC*
SAW Surface Acoustic Wave
SCART European connector definition for TV's and VCR's etc.
Schmitt Schmitt-trigger
SCI Special Circumstance Instructions PC term
SCNT1 Single Chip Network Termination 1 (NT1) AT&T*
SCSI* Small Computer System Interface. Pronounce as 'skuzi*'.
Scuzi* See SCSI*
SD Single density Floppy disk type. See DD*.
SDHT SDH/SONET Transceiver Siemens
SDRAM Synchronous DRAM*.
SECAM Systeme èn Coleur Avec Mémoire
SHARC Super Harvard ARchitecture Computer Analog
SICAT SIemens Concept Analog Telephone Siemens
SICOFI SIgnalling COdec* FIlter Siemens
SIO Serial Input Output Usually called UART
SIPO Serial in parallel out
SISO Serial in serial out
Skuzi* See SCSI*
SLAC Subscriber Line Audio processing interface AMD
SLIC Subscriber Line Interface Circuit
SLICOFI Subscriber Line Interface Circuit and signaling COdec* FIlter Siemens
SLIP Serial Line Interface Protocol Describes the protocol for making host-to-host connections using back-to-back serial ports (with crossover cable, of course). Can be used between two computers or to interconnect two hosts residing within a single computer. Robert L. Smith.
SM3 SONET 3:1 Multiplexer TranSwitch
SOT STS-1 Overhead Terminator TranSwitch
SPLD Simple Programmable Logic Device
SPST Single pole, single throw Switch type
SR Shift Register
SRAM Static RAM*
SS Single sided Floppy disk type
SSR Static Shift Register (Early designs were often dynamic) or Solid State Relay
STAF SDH Transceiver And Framer TranSwitch
Sync Synchronous The circuit works in phases. After a clock pulse the logic between any two registers gets enough time to stabilize and at the next clock pulse the results are loaded into the next register. Most complex circuits work in a synchronous mode. CPU* designers try to minimize the clock period as much as possible, which means that they are constantly busy trying to minimize the time that the at-that-moment slowest logic part needs. When a piece of logic can't be speeded-up they can decide to divide that part in two and when necessary include it twice. (See also RISC*).


Term Meaning Comments
Tera 10**12 or for computers 1024**4
Triple Containing 3 equal devices.
TSI Time Slot Interchanger AT&T*
TTL* Transistor Transistor Logic


Term Meaning Comments
UART Universal Asynchronous Receiver Transmitter
µC Micro* Controller Same as MCU*. It's a small micro* processor combined with a couple of peripherals on a chip
ULSI ultra large scale integration
UMPS* Modeling language for CPU* cores
µP Micro* Processor (=MPU* or CPU*)
UPI Universal Programmable Peripheral Interface Intel terminology
UPS Uninterruptable Power Supply This will keep your computer or other equipment running for a while more (about 15 minutes) after the 110/220V has gone, so it can still finish tasks and power down your computer in a controlled way. It may also guard against spikes on the 110/220V etc. It will usually contain some sort of accu. If you want to keep your computers running longer you'll need an aggregate running on some sort of fuel.
USART Universal Synchronous/Asynchronous Receiver/Transmitter This is a UART that can also work in synchronous mode. Synchronous means that the data isn't send in bytes with a start and stop bit around it, but the data bits are send continously. The bit clocks of the two USART*'s need to be synchronized in another way (for example via an extra line).
UTP Unshielded Twisted Pair This is a cheaper alternative for coax cable. Coaxial cable has the inner wire completely shielded by the other cable which is wooven around the inner one (and a tube of isolating material). This way magnetic fields can't influence the inner wire. Twisted pair cable has two wires that are wound around each other. This way both wires should experience the same fields and therefore both signals are distorted the same way. By subtracting the two signals from each other in the receiver the distortions are removed again.


Term Meaning Comments
VBAP Voice Band Audio Processor TI
VCA Voltage controlled amplifier
Vcc Main power supply Generally 5V
VCO* Voltage controlled oscillator
Vdd Secondary power supply
Vee Negative power supply
VESA Video Electronics Standards Association VGA-interface and Local-Bus-definition
V/F Voltage to Frequency (=VCO*)
VLSI Very Large Scale Integration
Vpp Programming power supply Generally higher then Vcc*
VRAM Video Random Access Memory Serial and/or dual* access(?)
VSS Also some sort of ground
VtoF Voltage to Frequency converter Same as VCO*



Term Meaning Comments
XOR Exclusive OR* The output is high when the number of high inputs is odd.


More abbreviations: Computing Dictionary

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