You’llalso have to indicate if your computer sends two stop bits to indicate
theend of abyte, instead of one, the default. These serial interface settings
are described in more detail in your Star LaserPrinter 4111Operations
Manual.
Serial interface:protocol
Finally,in Serialmode yourcomputer will useone oftwo protocolsto ensure
datais sentproperly. Protocol(sometimes alsocalled “handshaking”) means
“who sayswhat when”, and is the way your printer tells your computer it’s
ready to receive data. Your computer and printer communicate by sending
protocol control codes (they’re at the front of the ASCII table).
Someprogrammers call the XON and XOFFcontrol codes“kiss on and kiss
off’; otherscall the same protocolDC 1and DC3 (fordevice control). Either
way,these codes let your printer run the show, telling the computer when to
startand stop sending data.Your printer asks to havedata held back when its
memory isnearly full or when it senses an ERROR condition.
DTR (Data Terminal Ready) protocol does the same thing slightly differ-
ently. The printer sends acontinuous high-voltage signalover the cable as
long as it can accept data, but drops the voltage to say “whoa” to the
computer.
Look in your computer’s operations manual, in the section dealing with
communications protocols, to see which is best for your system. You can
stickto theprinter’s defaultsif yourcomputer doesnot usethe DTR,but does
use XON/XOFF.
2.2.2 Checking your connections
Yourcomputer and printer may have trouble communicating when you first
introducethem to each other. The quick way to find out if your settings and
printercable are working is to send your printer aprintout from your screen
(CTRL-P with MS-DOS).
When that doneyou will also have to press the print button on the printer,
which makes theprinter advance to anew sheet. No laser printer prints and
ejectsapage until it’s toldto feed aform, or until ithas received all the lines
the page can hold.
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