Page 36 - Engineering Digital Design

1.4 GLOSSARY OF TERMS, EXPRESSIONS, AND ABBREVIATIONS

Arithmetic shifter: a combinational shifter that is capable of generating and preserving
a sign bit.
Array algebra: the algebra of Boolean arrays and matrices associated with the automated
design of synchronous and STT machines.
Array logic: any of a variety of logic devices, such as ROMs, PLAs or PALs, that are
composed of an AND array and an OR array (see Programmable logic device or PLD).
ASIC: application-specific 1C.
ASM: algorithmic state machine.
Assert: activate.
Assertion level: activation level.
Associative law: a law of Boolean algebra that states that the operational sequence as
indicated by the location of parentheses in a p-term or s-term does not matter.
Associative pattern: an XOR pattern in a K-map that allows a term or variable in an
XOR or EQV function to be looped out (associated) with the same term or variable in
an adjacent cell provided that the XOR or EQV connective is preserved in the process.
Asynchronous: clock-independent or self-timed — having no fixed time relationship.
Asynchronous input: an input that can change at any time, particularly during the sam-
pling interval of the enabling input.
Asynchronous override: an input such as preset or clear that, when activated, interrupts
the normal operation of a flip-flop.
Asynchronous parallel load: the parallel loading of a register or counter by means of
the asynchronous PR and CL overrides of the flip-flops.
Augend: an operand that is added to the addend in an addition operation.
Barrel shifter: a combinational shifter that only rotates word bits.
Base: radix. Also, one of three regions in a BIT.
Basic cell: a basic memory cell, composed of either cross-coupled NAND gates or cross-
coupled NOR gates, used in the design of other asynchronous FSMs including flip-flops.
BCD: binary coded decimal.
BCH: binary coded hexadecimal.
BCO: binary coded octal.
BDD: binary decision diagram.
Bidirectional counter: a counter that can count up or down.
Binary: a number system of radix 2; having two values or states.
Binary code: a combination of bits that represent alphanumeric and arithmetic informa-
tion.
Binary coded decimal (BCD): a 4-bit, 10-word decimal code that is weighted 8, 4, 2, 1
and that is used to represent decimal digits as binary numbers.
Binary coded hexadecimal (BCH): the hexadecimal number system used to represent
bit patterns in binary.
Binary coded octal (BCO): the octal number system used to represent bit patterns in
binary.
Binary decision diagram (BDD): a graphical representation of a set of binary-valued
decisions, beginning with an input variable and proceeding down paths that end in either
logic 1 or logic 0.
Binary word: a linear array of juxtaposed bits that represents a number or that conveys
an item of information.