Serialinterface:rate
Ifyou askforthe Serialinterfaceyou’llhavetotellyour printermoreabout
howthe datawillbe comingin-in particularitsrateand unitsize andthe
meaningsofany specialbits.
TheRate parameterspecifieshow fast datawill be arriving,measuredin
baud(namedaftertheFrenchcommunicationsengineerJeanBaudot).Pick
anyof the followingdatatransferrates:
300baud
600baud
1200baud
2400baud
4800baud
9600baud (thedefault)
19200baud.
Roughly,onecharacter secondworksoutto11baud.If you’renotsurehow
fastyour computer will transmit,the general rule is to experiment.Try
sendingapagetoprint atthe highestspeed,andworkyour waydownuntil
theprinter’soutputlooks OK.
Serialinterface:specialbits
InSerialmodeyou’llalsohaveto specify ifyourcomputersends databits
ingroups ofseven (mostcomputerssendeight,the defaultfor abyte).
Sometimesanextra bitgets appendedto makethe sum of allbits in each
characteralwaysoddoreven;that’scalledparity. Aparitybitcanhelp spot
transmissionerrors.Ifyourcomputersendsthatextraparitybit,you’llhave
to say whetherit produces an even or odd numberof “on” bits in the
character.
You’llalsohaveto indicateifyourcomputersendstwostop bitstoindicate
theend ofabyte, insteadofone, thedefault.Theseserialinterfacesettings
aredescribedinmoredetailinyourStarfuserPrinter4 @erationsMan~l.
Serialinterface:protocol
Finally,in Serialmode your computerwilluse one of three profocoZsto
ensuredata is sentproperly.Protocol (sometimesalsocalled “handshak-
ing”)means“who sayswhatwhen”, andis the wayyourprinter tellsyour
computerit’sreadytonxeivedata.Yourcomputerandprintercommunicate
bysendingprotocolcontrolcodes(they’reat thefront ofthe ASCIItable).
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