Laser Printer Applications Manual

The Rateparameterspecifieshow fast data will be arriving,measuredin

baud(namedaftertheFrenchcommunicationsengineerJeanBaudot).pick

anyof thefollowingdatatransferrates:

300baud

600baud

1200baud

2400baud

4800baud

9600baud(thedefault)

19200baud.

Roughly, one character asecond worksoutto 11baud.1fyou‘renot sure how

fast your computer will transmit, the general rule is to cxpcrimcnt. Try

sending a page to print at the highest speed, and

workyourwaydownuntil

thepnntcr’soutputlooksOK.

Serial interface: specialbits

In-Serialmodeyou’llalsohaveto specifyif yourcomputersendsdatabits

in groupsof seven(mostcomputerssendeight,thedefaultfor a byte).

Somelimesan extrabit gets appendedto makethe sumof all bits in each

characteralwaysoddoreven;that’scalledparity. Aparitybitcanhelpspot

transmissionerrors.Ifyourcomputersendsthatextraparitybit,you’llhave

to say whether it produces an even or odd number of “on” bits in the

character.

You’llalsohavetoindicateifyourcomputersendstwostopbitsto indicate

thecndof a byte,insteadofone,thedefault.Theseserialintcrfaccsettings

aredcscnbedinmoredetailinyourStarLaserPrinter8OperationsManual.

Serial interface: protocol

Finally,in Serialmodeyour computerwill use one of threeprotocolsto

ensure data is sent properly. Protocol (sometimes also called “handshak-

ing”)means“whosayswhatwhen”,andis the wayyourprintertellsyour

computerit’sreadytoreceivedata.Yourcomputerandpnntercommunicate

by sendingprotocolcontrolcodes(they’reatthe frontof theASCIItable).

SomeprogrammerscalltheXONand XOFFcontrolcodes“kissonandkiss

off’;otherscallthesameprotocolDC1andDC3(fordevicecontrol).Either

way,thesecodesletyourprinterruntheshow,tellingthecomputerwhento

startandstopsendingdata.Yourprinterasksto havedataheldbackwhen

its mcmoryis nearlyfullor whenit sensesan ERRORcondition.