
Section 7. Installation
209
MarksandSpaces
RS‐232signallevelsareinvertedlogiccomparedtoTTL.Thedifferent
levelsarecalledmarksandspaces.Whenreferencedtosignalground,
thevalidRS‐232voltagelevelforamarkis‐3to‐25,andforaspaceis
+3to+25with‐3to+3defin
edasthetransitionrangethatcontainsno
information.Amarkisalogic1andnegativevoltage.Aspaceisalogic0
andpositivevoltage.
MSB
Mostsignificantbit(theleadingbit).
RS‐232C
Referstothestandardusedtodefinethehardwaresignalsandvoltage
levels.TheCR3000supportsseveraloptionsofseriallogicandvoltage
levelsincludingRS‐232logicatTTLlevelsandTTLlogicatTTLlevels.
RX
Receive
SP
Space
Startbit
Isthebitusedtoindicatethebeginningofdata.
Istheendofthedatabits.Thestopbitcanbe1,1.5or2.
TX
Transmit
7.8.8.5 CRBasic Programming
To transmit or receive RS-232 or TTL signals, a serial port (see table CR3000
Serial Ports
(p. 207) ) must be opened and configured through CRBasic with the
SerialOpen() instruction. The SerialClose() instruction can be used to close the
serial port. Below is practical advice regarding the use of SerialOpen() and
SerialClose(). Program CRBasic example Receiving an RS-232 String
(p. 215)
shows the use of SerialOpen(). Consult CRBasic Editor Help for more
information.
SerialOpen(COMPort,BaudRate,Format,TXDelay,BufferSize)
• COMPort — Refer to CRBasic Editor Help for a complete list of COM ports
available for use by SerialOpen().
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