Star Micronics manual 3Howyour Iaserprinter communicates, TheStar LaserPrinter4 is a computer

1.2.3Howyour Iaserprinter communicates

Your computercommunicateswith the Star LaserPrinter4 througheither apardef cableor one of two kindsof serialcable.Theprinter’sinterjzce, the link or boundaryit shares with your computer,defines whether the printerwill acceptcharactersandcommandsfromyourcomputerone byte or one bit at a time.

A bit is the smallestunitof computeror printermemory.It haseithera low or highelectriccharge,whichwe representwiththe digitsOand 1.Usually eight adjacentbits are grouped to form a byte. Since a byte normally representsone character,this stringof bits- O1OOOOO1mightrepresent— the letterA.

The serial interfaceacceptsjust one bit at a time from your computer.A parallelinterfacecanhandlea wholebyteatonce,bymovingdatabitsside- by-sidealongseparatewires.Youchoosewhichinterfacemethodyouwant to useby selectingit on the controlpanel,as explainedin yourStarLuser- Printer4 OperationsManual.

1.2.4TheStar LaserPrinter4 is a computer

The StarLaserPrinter4 first maps the charactemto be printedinto its own randomaccessmemory(RAM).Thatis, theprinterbuildsa “picture”in its memorycorrespondingto thepageyouwantto print.Whenthat’sdonethe printercan reproducethepageontopaperon itsown,lettingyourcomputer get on with other work.

YourStarLaserPrinter4 comeswithone megabyteof RAM—the equiva- lent of aboutone millioncharacters.A StarLaserPrinter4 optionlets you adda secondmegabyteofRAMif, say,youneedto mapfull-pagegraphics or stem morefonts. AccompanyingallthatRAMis another512kilobytes of read onlymemory(ROM),containinga libraryof internalfontsandthe programsthat let the Star LaserPrinter4 emulateother printers.

An Intel 80960KA computer chip controls both the memory and the printingmechanisminthepnnter, calledtheprintengine.Theprinterstores

awhole page in RAM before printing it. (If a page is so dense that it overflowsmemory-a mostunlikelyevent—theStarLaserPrinter4 prints the page on two sheets.)

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