SomepmgrammemcalltheXONand XOFFcontrolcodes“kissonandkiss
off’ otherscallthesameprotocolDC1andDC3(fordevicecontrol).Either
way,thesecodesletyourprinterruntheshow,tellingthecomputerwhento
startand stopsendingdata.Yourprinteraskstohavedataheldbackwhen
its memoryis nearlyfull or whenit sensesan ERRORcondition.
DTR(DataTerminalReady)protocoldoesthe samethingslightlydiffer-
ently.Theprintersendsa continuoushigh-voltagesignaloverthe cableas
long as it can accept data, but drops the voltage to say “whoa” to the
computer.
Look in your computer’soperationsmanual,in the sectiondealingwith
communicationsprotocols,to see whichis bestfor yoursystem.You can
sticktotheprinter’sdefaultsifyourcomputerdoesnotusetheDTR,butdoes
use
XON/XOFF.
2.2.2 Checkingyour connections
Yourcomputerandpnntermayhavetroublecommunicatingwhenyoufirst
introducethemtoeachother.Thequickwayto findoutif yoursettingsand
printercableareworkingisto sendyourprintera printoutfromyourscreen
(CTRL-PwithMS-DOS).
Whenthat’sdoneyouwillalsohaveto presstheprintbuttonontheprinter,
whichmakestheprinteradvanceto a newsheet.Nolaserprinterprintsand
ejectsapageuntilit’stoldtofeeda form,oruntilithasreceivedallthelines
thepage canhold.
If yourStar LaserPrinter4 doesn’tprintwhat’son the computerscreen,
recheck your connectionsand interface settings. With an applications
programlikeLotus1–2–3orMicrosoftWord,youuseaprintersetuproutine
to match your computerwith yourprinter’soperatingcharacteristics.So
double-checkyoursoftwaresettings;yourcomputer’soutput,forexample,
mightnot be goingto theproperport.
2.2.3 Printeremulations
OK, you’vegot yourprinterand computerconnectedproperly.Now let’s
focuson how yourprinterworks.
Your Star LaserPrinter4 understandsand uses the same commandsas
severalearlierkindsof printers.Yourprinterworksby emulatingone of
these:
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