IEEE 91A : 1991

1 Introduction
1.1 Purpose
1.2 Scope
1.3 Revised or deleted symbols
1.4 Applicable documents
1.4.1 Industry standards
1.4.2 Military standards
1.4.3 International standards
1.5 Definitions
1.5.1 Logic state
1.5.1.1 0-state
1.5.1.2 1-state
1.5.1.3 External logic state
1.5.1.4 Internal logic state
1.5.2 Logic level
1.5.2.1 High (H) level
1.5.2.2 Low (L) level
1.5.3 Logic conventions and polarity indication
1.5.3.1 Positive logic convention
1.5.3.2 Negative logic convention
1.5.3.3 Direct polarity indication
1.5.4 Logic function
1.5.4.1 Combinational logic function
1.5.4.2 Sequential logic function
1.5.4.3 Bistable logic function (flip-flop)
1.5.5 Element
1.5.6 Qualifying symbol
1.5.7 Dependency notation
1.5.8 Distributed function (dot logic, wired logic)
1.6 Orientation of qualifying symbols
2 Symbol construction
2.1 Composition of a symbol
2.1.1 General composition
2.1.2 Nonstandard information
2.1.3 Logic states of outputs
2.2 Outlines
2.3 Use and combination of outlines
2.3.1 Embedded and abutted elements
2.3.2 Common control block
2.3.2.1 Weighted arrays
2.3.3 Common output element
2.3.3.1 Array of common output elements
3 Qualifying symbols associated with inputs,
         outputs, and other connections
3.1 Negation, polarity, and dynamic input symbols
3.2 Internal connections
3.3 Symbols inside the outline
3.4 Subsidiary (formerly nonlogic) connections and
         signal-flow indicators
4 Dependency notation
4.1 General explanation
4.2 Summary of types of dependencies
4.2.1 Comparison of C, EN, and M effects on inputs
4.3 Application of dependency notation
4.3.1 General techniques and conventions
4.3.2 AND dependency (G dependency)
4.3.3 OR dependency (V dependency)
4.3.4 Negate dependency (N dependency)
4.3.5 Interconnection dependency (Z dependency)
4.3.6 Transmission dependency (X dependency)
4.3.7 Control dependency (C dependency)
4.3.8 Set and reset dependencies (S and R
         dependencies)
4.3.9 Enable dependency (EN dependency)
4.3.10 Mode dependency (M dependency)
4.3.11 Address dependency (A dependency)
4.4 Special techniques used in dependency notation
4.4.1 Use of a coder to produce affecting inputs
4.4.2 Use of bit-grouping to produce affecting inputs
4.4.3 Order of input labels
4.4.4 Order of output labels
4.4.5 Labelled inputs other than D inputs having
         inherent storage
5 Combinational and sequential elements
5.1 Basic combinational elements basic rule
5.2 Buffers with special amplification, drivers,
         receiveres, and bidirectional switches
5.3 Elements exhibiting hysteresis
           Schmitt triggers
           Bithreshold detectors
5.4 Coders
5.4.1 Indicating input and output codes in general
         qualifying symbol
5.4.1.1 Summing codes
5.4.1.2 Direct-indication codes
5.4.1.3 Codes representing symbols
5.4.2 Replacement of X and Y by indications of the
         input code or the output code
5.4.3 Use of coding tables
5.4.4 Examples of coders
5.5 Signal-level converters
5.6 Multiplexers and demultiplexers
5.7 Arithmetic elements
5.8 Delay elements
5.9 Basic bistable elements
5.10 Bistable elements with special switching
         properties
5.11 Monostable elements
5.12 Astable elements
5.13 Shift registers and counters
5.14 Memories
5.15 Display elements
6 Symbols for highly complex functions
6.1 General symbol and basic rules
6.1.1 General
6.1.2 Input and output designation
6.1.3 Negated terminal names
6.1.4 Functional grouping
6.1.5 Label grouping
6.1.6 Long character strings
6.1.7 Consecutive labels and terminal numbers
6.1.8 Function tables and truth tables
6.1.9 Bus indicators
6.2 Internal diagrams
6.2.1 General
6.2.2 Data-path representation
6.3 Examples of complex elements
Tables
3.1 Commonly used logical signal designations
4.1 Summary of dependency notation
Appendices
A Recommended symbol proportions
B Revised or deleted symbols
C Composite chart showing relationship of graphic
         symbols for logic diagrams from
         ANSI/IEEE 91-1982 and the superseded standards
D Integrated circuits used as examples commercial
         part numbers versus symbol numbers
Index

Contains graphic symbols for representing logic functions or physical devices capable of carrying out logic functions. Coverage includes: logic conventions and polarity indication; combinational logic function; sequential logic function; logic states of outputs; orientation of qualifying symbols; application of dependency notation; bistable elements with special switching properties; shift registers and counters; multiplexers and demultiplexers; consecutive labels and terminal numbers.