eZ80
®
CPU
User Manual
UM007714-0908 Glossary
383
Arithmetic Logical Unit (ALU). the element that can perform the basic data manipulations in the central
processor. Usually, the ALU can add, subtract, complement, negate, rotate, AND, and OR.
array. An arrangement of elements in one or more dimensions. In a programming language, an aggregate
that consists of data objects with identical attributes, each of which may be uniquely referenced by
subscription.
AS. Address Strobe.
ASCII. Acronym for American Standard Code for Information Interchange. The standard code used for
information interchange among data processing systems, data communications systems, and associated
equipment in the United States.
ASYNC. Asynchronous Communication Protocol.
ASYNCA. Asynchronous Channel A.
ASYNCB. Asynchronous Channel B.
asynchronous. An event or device that is not synchronous with CPU timing (or other process).
Asynchronous Transfer Mode (ATM). A high-speed multiplexing and switching method utilizing fixed-
length cells of 53 octets to support multiple types of traffic. ATM, specified in international standards, is
asynchronous in the sense that cells carrying user data need not be periodic. A method used for
transmitting voice, video, and data over high-speed local area networks.
asynchronous transmission. Data transmission in which the instant that each character, or block of
characters, starts is arbitrary; once started, the time of occurrence of each signal representing a bit within
the character, or block, has the same relationship to significant instants of a fixed time frame.
AT commands. A de facto standard for modem commands from an attached CPU, used in most 1,200 and
2,400 b/s modems.
AT command set. The character set used in modem control strings. Characters include the alphabet from
A through T plus a special carriage return, <CR>.
ATE. Automatic Test Equipment.
ATM. See Asynchronous Transfer Mode.
AV
DD
. Analog power.
baud. A unit of measure of transmission capacity. The speed at which a modem can transmit data. The
number of events or signal changes that occur in one second. Because one event can encode more than one
bit in high-speed digital communications, baud rate and bits per second are not always synonymous,
especially at speeds above 2400 bps.
baud rate. A unit of measure of the number of state changes (from 0 to 1 or 1 to 0) per second on an
asynchronous communications channel.
big-endian. A computer architecture in which, within a given multibyte numeric representation, the most
significant byte contains the lowest address (the word is stored “big-end-first”).
binary (b). A number system based on A binary digit is a bit.
bit. binary digit—a digit of a binary system. It contains only two possible values: 0 or 1.
Bit Error Ratio (BER). The number of erroneous bits divided by the total number of bits transmitted,
received, or processed over some stipulated period.
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