Logix5000 Controllers General Instructions - SLAC Confluence

Chapter 18ASCII Serial Port Instructions(ABL, ACB, ACL, AHL, ARD, ARL, AWA, AWT)IntroductionUse the ASCII serial port instructions to read and writeASCII characters.IMPORTANTTo use the ASCII serial port instructions, you must configure theserial port of the controller. See the Logix5000 ControllersCommon Procedures, publication 1756-PM001.If You Want To For Example Use ThisInstructiondetermine when the buffer containstermination characterscount the characters in the bufferclear the bufferclear out ASCII Serial Portinstructions that are currentlyexecuting or are in the queueobtain the status of the serial portcontrol linesturn on or off the DTR signalturn on or off the RTS signalread a fixed number of charactersread a varying number of characters,up to and including the first set oftermination characterssend characters and automaticallyappend one or two additionalcharacters to mark the end of thedatasend characterscheck for data that containstermination characterscheck for the required number ofcharacters before reading the buffer• remove old data from the buffer atstart-up• synchronize the buffer with adeviceABLACBACLAvailable In TheseLanguagesrelay ladderstructured textrelay ladderstructured textrelay ladderstructured textcause a modem to hang up AHL relay ladderread data from a device that sendsthe same number of characters eachtransmissionread data from a device that sends avarying number of characters eachtransmissionsend messages that always use thesame termination character(s)send messages that use a variety oftermination charactersARDARLAWAAWTstructured textrelay ladderstructured textrelay ladderstructured textrelay ladderstructured textrelay ladderstructured textSee Page575578581583587591595600571 Publication 1756-RM003I-EN-P - January 2007