A Digital SystemDesign Language (DDL)

Successful design andmanufacture offuture digital systems will depend upontheavailability ofasuitable design lan- guage. Aprecise, concise language ispresented whichfacilitates the specification ofcomplex digital systems. Thelanguage 1)isinde- pendent ofanyparticular technology, design procedure, machine organization, etc., 2)allows specification atdifferent levels ofdetail fromarchitecture todetailed Boolean equations, and3)maybecom- piled intomanufacturing information. Itssyntax andsemantics per- mitdocuments withanorganization whichparallels theblock struc- tureofthesystems theyspecify. Syntax andsemantics ofthelanguage aredefined. Pragmatics of thelanguage aredemonstrated throughout thepaper withexamples. IndexTerms-Automata, Boolean equations, computer design, declarations, design automation, design language, digital systems, syntax andsemantics, system design, system model. I.INTRODUCTION S PECIFYING,documenting, andcontrolling the design ofdigital systems areproblems ofincreasing severity assuchsystems continue togrowinsize andcomplexity. Wilkes andStringer (2)first recognized thatasuitable design language could greatly reduce the magnitude ofthese problems andleadtoacomplete, precise, yetconcise description ofdigital systems. Un- fortunately, their contribution ismostly oriented to- wardthemachine thatthey weredeveloping atthetime andisnotgenerally useful. Reed's register transfer language (3)- (5) hasreceived widerdistribution. Itiseasily learned, rather generally applicable, anditsstatements associate directly with hardware. However, acomplete description ofasystem cannot beexpressed inthis language, noprovisions exist forpartitioning systems, andthesmall vocabulary of thelanguage necessitates theuseofmanysymbols. Determining thesequence ofevents whicharetotake place inasystem fromaReed-language description may notbeaneasytask. TheLDT language ofBurroughs (6)- (9) andthe Sequence ChartofIBM (8)supplement Reed's lan- guagesothatacomplete description ofasystem canbe given. TheSequence Chartdisplays timing andse- quencing information inagraphic manner.Bothlan- guages arebackedbycomputer programs whichgen- eratelogic equations fromReed-like statements. The LDT systemusesprescribed logic structures toanex- tent, butdoestiming analysis. Thegraphic natureof