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How your Iaserprinter communicates
Yourcomputercommunicates withthe StarLaserPrinter8 througheithera
parallelcableor one of two kindsof serialcable.The printer'sinterj2ace,
the link or boundaryit shares with your computer,defines whether the
printerwill acceptcharactersandcommandsfrom yourcomputerone byte
or one bit at a time.
A bit is the smallestunitof computeror printermemory.It haseithera low
or highelectriccharge,whichwe representwiththedigitsOand 1.Usually
eight adjacentbits are grouped to form a byte. Since a byte normally
representsonecharacter,this stringof bits- O1OOOOO— m ightrepresent
the letterA.
The serial interfaceacceptsjust one bit at a time from your computer.A
parallelinterfacecanhandlea wholebyteatonce,bymovingdatabitsside-
by-sidealongseparatewires.Youchoosewhichinterfacemethodyouwant
to use by selecting it on the operator panel, as explained in your Star
LaserPrinter8 OperationsManual.
The Star LaserPrinter 8 is a computer
The Star LaserPrinter8 first maps thecharactersto be printedinto its own
randomaccessmemory(RAM).Thatis, theprinterbuildsa "picture"in its
memorycorresponding to thepageyouwantto print.Whenthat'sdonethe
pnntercan reproducethepageontopaperon itsown,lettingyourcomputer
get on'with other work.
YourStarLaserPrinter8 comeswithone megabyteof RAM—theequiva-
lent of aboutone millioncharacters.A Star LaserPrinter8 optionlets you
adda secondmegabyteofRAMif, say,youneedto mapfull-pagegraphics
or storemorefonts. Accompanying allthatRAMis another512 kilobytes
of read onlymemory(ROM),containinga libraryof internalfontsand the
programsthat let the Star LaserPrinter8 emulateotherprinters.
AMotorola68000computerchipcontrolsboththememoryandtheprinting
mechanismintheprinter,calledtheprintengine.Theprintcrstoresa whole
page in RAM before printingit. (If a page is so dense that it overflows
memory-a mostunlikelyevent—theStarLaserPrinter8printsthepageon
two sheets.)
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