Serialinterface:rate
If youaskfortheSerialinterfaceyou’llhaveto tellyourprintermoreabout
howthedatawillbecomingin-in particularits rateandunitsizeandthe
meaningsof any specialbits.
The Rate parameterspecifieshow fastdata will be arriving,measuredin
baud(namedaftertheFrenchcommunicationsengineerJeanBaudot).Pick
anyof the followingdatatransferrates:
300baud
600baud
1200baud
2400baud
4800baud
9600baud(thedefault)
19200baud.
Roughly,onecharacter secondworksoutto11baud.Ifyou’renotsurehow
fast your computerwill transmit,the generalrule is to experiment.Try
sendingapageto printatthehighestspeed,andworkyourwaydownuntil
theprinter’soutputlooksOK.
Serialinterface:specialbits
InSerialmodeyou’llalsohaveto specifyif yourcomputersendsdatabits
in groupsof seven(mostcomputerssendeight,the defaultfor a byte).
Sometimesan extrabit getsappendedto makethe sumof all bits in each
characteralwaysoddoreven; that’scalledparity. Aparitybitcanhelp spot
transmissionerrors.Ifyourcomputersendsthatextraparitybit,you’llhave
to say whether it produces an even or odd number of “on” bits in the
character.
You’llalsohavetoindicateif yourcomputersendstwostopbitstoindicate
theendof a byte,insteadof one,thedefault.Theseserialinterfacesettings
aredescribedinmoredetailinyourStarfuserPrinter4 @erationsMan~l.
Serialinterface:protocol
Finally,in Serialmodeyour computerwill use one of threeprofocoZsto
ensuredata is sent properly.Protocol(sometimesalso called“handshak-
ing”)means“whosayswhatwhen”,andis thewayyourprintertellsyour
computerit’sreadytonxeivedata.Yourcomputerandprintercommunicate
by sendingprotocolcontrolcodes(they’reatthefrontofthe ASCIItable).
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