EDSTRG44PLCC datasheet(31/78 Pages) TI

31 / 78 page

TIMING CONVENTIONS

1–23

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• HOUSTON, TEXAS 77251–1443

timing conventions

This section defines the timing parameters, including cycle time, hold time, pulse duration, and others.

time intervals

New or revised data sheets in this book use letter symbols in accordance with standards recently adopted by

JEDEC, the IEEE, and the IEC. Two basic forms of symbols are used. The first form is used usually when

intervals can be classified easily as cycle, hold, setup, transition, valid, or delay times and for pulse durations.

The second form can be used generally, but in this book the second form is primarily for time intervals not easily

classifiable. The second (unclassified) form is described first. Since some manufacturers use this form for all

time intervals, symbols in the unclassified form are given with the examples for most of the classified time

intervals.

unclassified time intervals

Generalized letter symbols can be used to identify almost any time interval without classifying it using traditional

or contrived definitions. Symbols for unclassified time intervals identify two signal events listed in from-to

sequence using the format:

t(AB-CD)

Subscripts A and C indicate the names of the signals for which changes of state or level or establishment of

state or level constitute signal events assumed to occur first and last, respectively, that is, at the beginning and

end of the time interval.

Subscripts B and D indicate the direction of the transitions and/or the final states or levels of the signals

represented by A and C, respectively. One or two of the following is used:

H = high or transition to high

L = low or transition to low

V = a valid steady-state level

X = unknown, changing, or “don’t care” level

Z = high-impedance (off) state

The hyphen between the B and C subscripts is omitted when no confusion is likely to occur.

classified time intervals

Because of the information contained in the definitions, frequently the identification of one or both of the two

signal events that begin and end the intervals can be shortened significantly compared to the unclassified forms.

For example, it is not necessary to indicate in the symbol that an access time ends with valid data at the output.

However, if both signals are named (e.g., in a hold time), the from-to sequence is maintained.

cycle time

The time interval between the start and end of a cycle.

NOTE: For each cycle time (tc), the value given represents the minimum time interval required to complete one cycle of the given function

(e.g., read, write, etc.) correctly.

Example symbology:

Classified

Description

Cycle time, (SYSCLK)

tc(SPC)

Cycle time, (SPICLK)

tc(SCC)

Cycle time, (SCICLK)

EDSTRG44PLCC Datasheet(PDF) 31 Page - Texas Instruments

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