IEEE 991-1986 pdf free.An American National Standard IEEE Standard for Logic Circuit Diagrams.
IEEE 991 of this standard is to provide standard practices and information for use in the preparation of diagramsdepicting logic functions.
This standard provides guidelines for preparation of diagrams depicting logic functions. It includes definitions,requirements for assignment of logic levels， application of logic symbols，presentation techniques， and labelingrequirements with typical examples. The techniques are presented in the context of electrical/electronic systems, butalso may be applied to nonelectrical systems (for example, pneumatic, hydraulic, or mechanical).
The following definitions are for use with this standard. For other use and for definitions not contained herein, seeANSI/IEEE Std 100-1984 6
graphic symbol:A figure,mark, or character conventionally used on a diagram, document, or other display torepresent an item or a concept.
logic symbol: A graphic symbol that represents a logic function.
qualifying symbol: A graphic symbol added to another to provide additional information. For a logic element, agraphic symbol added to the basic outline to designate the overall logic characteristics of the element or the physicalor logic characteristics of an input or output of the element.
negation bar: A line over a signal label that indicates logic inversion of that signal.
element: As used within this standard, a representation of all or part of a function within a single outline, which may,in turn, be subdivided into smaller elements representing subfunctions of the overall function. Alternatively, thefunction so represented.
logic circuit diagram: A circuit diagram that predominantly uses symbols for logic functions to depict the overalfunction of a circuit.
basic logic diagram: A logic circuit diagram that depicts, in simple form, the intended function of a circuit.It doesnot necessarily contain constructional or engineering information, nor does it represent exactly the final physicalform.
detailed logic diagram: A logic circuit diagram that depicts, in detail, a circuit as actually implemented.Ilt containsinformation that can be used for manufacturing or maintenance purposes, but it does not necessarily includeengineering information that is not concerned with logic functions.
logic state: One of two possible abstract states that may be taken on by a logic (binary) variable.
0-state:The logic state represented by the binary number 0 and usually standing for an inactive or false logiccondition.
1-state:The logic state represented by the binary number 1 and usually standing for an active or true logic condition.logic level: Any level within one of two nonoverlapping ranges of values of a physical quantity used to represent thelogic states.IEEE 991 pdf download.