Page 56 - Engineering Digital Design

1.4 GLOSSARY OF TERMS, EXPRESSIONS, AND ABBREVIATIONS 27

State: a unique set of binary values that characterize the logic status of a machine at some
point in time.
State adjacency set: any 2" set of logically adjacent states of an FSM.
State code assignment: unique set of code words that are assigned to an FSM to charac-
terize its logic status.
State diagram: the diagram or chart of an FSM that shows the state sequence, branching
conditions, and output information necessary to describe its sequential behavior.
State machine: a finite state machine (FSM). A sequential machine.
State identifier: any symbol (e.g., alphabetical) that is used to represent or identify a
state in a state diagram.
State table: tabular representation of a state diagram.
State transition table: (see excitation table).
State variable: any variable whose logic value contributes to the logic status of a machine
at any point in time. Any bit in the state code assignment of a state diagram.
Static hazard: an unwanted glitch in an otherwise steady-state signal that is produced by
an input change propagating along asymmetric path delays through inverters or gates.
Static-1 hazard: a glitch that occurs in an otherwise steady-state 1 output signal from SOP
logic due to a change in an input for which there are two asymmetric paths (delay-wise)
to the output.
Static-0 hazard: a glitch that occurs in an otherwise steady-state 0 output signal from POS
logic due to a change in an input for which there are two asymmetric paths (delay-wise)
to the output.
Static RAM: a nonvolatile form of RAM — does not need periodic refreshing to hold its
information.
Steering logic: logic based primarily on transmission gate switches.
S-term: a Boolean sum term — one containing only ORed literals.
Stretcher: an input conditioning device that catches a short input signal and stretches it.
STT: single transition time.
Stuck-at fault: an input to a logic gate that is permanently stuck at logic 0 or logic 1
because of a shorted connection, an open connection, or a connection to either ground
or a voltage supply.
Substrate: the supporting or foundation material in and on which a semiconductor device
is constructed.
Subtracter: a digital device that subtracts one binary word from another to give a differ-
ence and borrow.
Subtrahend: the operand being subtracted from the minuend in a subtraction operation.
Sum-of-products (SOP): the ORing of ANDed terms in a Boolean expression.
Sum rule: a rule in state diagram construction that requires that all possible branching
conditions be accounted for.
Switching speed: a device parameter that is related to its propagation delay time.
Synchronizer circuit: a logic circuit (usually a D flip-flop) that is used to synchronize
an input with respect to a clock signal.
Synchronous machine: a sequential machine that is clock driven.
Synchronous parallel load: parallel loading of a register or counter via a clock signal to
the flip-flops.
System level design: a design that includes controller and data path sections.
Tabular minimization: a minimization procedure that uses tables exclusively.