How your Iaserprinter communicates
YourcomputercommunicateswiththeStarLaserPrinter8througheithera
parallelcableor oneof twokindsof serialcable.Theprinter’sinterj2ace,
the link or boundaryit shares with your computer,defineswhetherthe
printerwillacceptcharactersandcommandsfromyourcomputeronebyte
or onebit at a time.
Abitisthesmallestunitofcomputerorprintermemory.It haseitheralow
orhighelectriccharge,whichwerepresentwiththedigitsOand 1.Usually
eight adjacentbits are groupedto form a byte. Since a byte normally
representsonecharacter,thisstringofbits- O1OOOOO—mightrepresent
theletterA.
The serialinterfaceacceptsjust one bit at a time fromyourcomputer.A
parallelinterfacecanhandleawholebyteatonce,bymovingdatabitsside-
by-sidealongseparatewires.Youchoosewhichinterfacemethodyouwant
to use by selectingit on the operatorpanel, as explainedin your Star
LaserPrinter8 OperationsManual.
The Star LaserPrinter 8 is a computer
TheStarLaserPrinter8 firstmapsthecharactersto beprintedintoitsown
randomaccessmemory(RAM).Thatis,theprinterbuildsa“picture”inits
memorycorrespondingtothepageyouwanttoprint.Whenthat’sdonethe
pnntercanreproducethepageontopaperonitsown,lettingyourcomputer
geton’withotherwork.
YourStarLaserPrinter8comeswithonemegabyteofRAM—theequiva-
lentof aboutonemillioncharacters.A StarLaserPrinter8 optionletsyou
addasecondmegabyteofRAMif,say,youneedtomapfull-pagegraphics
orstoremorefonts. AccompanyingallthatRAMis another512kilobytes
ofreadonlymemory(ROM),containingalibraryof internalfontsandthe
programsthatlettheStarLaserPrinter8 emulateotherprinters.
AMotorola68000computerchipcontrolsboththememoryandtheprinting
mechanismintheprinter,calledtheprintengine.Theprintcrstoresawhole
pagein RAM beforeprintingit. (If a pageis so densethat it overflows
memory-a mostunlikelyevent—theStarLaserPrinter8printsthepageon
two sheets.)
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