Digital Logic Design, 4th Edition

Appendix Functional logic symbols

A.1 Introduction

Over a period of more than twenty-five years, during which time the technology of digital systems has been developing at an unprecedented rate, methods of depicting digital systems in circuit diagrams using standardised logic symbols have similarly been developing. This has resulted in two completely separate sets of logic gate symbols that can be used in drawing circuit diagrams, the ‘old’ or ‘conventional’ system and the ‘new’ or ‘functional’ logic symbols. In the UK the ‘new’ standards for drawing circuit diagrams appear in BS 3939, Section 21, and in the USA they appear in IEEE Std. 91/ANSI Y32.14 and IEC publication 617–12. Perhaps the most significant advantage of the standardized system ...