Logix5000 Controllers General Instructions - SLAC Confluence

596 ASCII Serial Port Instructions (ABL, ACB, ACL, AHL, ARD, ARL, AWA, AWT)SERIAL_PORT_CONTROL StructureMnemonic Data Type Description.EN BOOL The enable bit indicates that the instruction is enabled..EU BOOL The queue bit indicates that the instruction entered the ASCII queue..DN BOOL The done bit indicates when the instruction is done, but it is asynchronous to the logic scan..RN BOOL The run bit indicates that the instruction is executing..EM BOOL The empty bit indicates that the instruction is done, but it is synchronous to the logic scan..ER BOOL The error bit indicates when the instruction fails (errors)..FD BOOL The found bit does not apply to this instruction..LEN DINT The length indicates the number of characters to send..POS DINT The position displays the number of characters that were sent..ERROR DINT The error contains a hexadecimal value that identifies the cause of an error.Description:The AWA instruction:• sends the specified number of characters (Serial Port ControlLength) of the Source tag to the device that is connected to theserial port of the controller• adds to the end of the characters (appends) either one or twocharacters that are defined in the Controller Properties dialogbox, User Protocol tabTo program the AWA instruction, follow these guidelines:1. Configure the serial port of the controller:a. Does your application also include ARD or ARL instructions?IfYesNoThenSelect User modeSelect either System or User modeb. Define the characters to append to the data.2. This is a transitional instruction:• In relay ladder, toggle the rung-condition-in from cleared toset each time the instruction should execute.• In structured text, condition the instruction so that it onlyexecutes on a transition. See .Publication 1756-RM003I-EN-P - January 2007