Logix5000 Controllers General Instructions - SLAC Confluence

ASCII Serial Port Instructions (ABL, ACB, ACL, AHL, ARD, ARL, AWA, AWT) 5853. 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 .Arithmetic Status Flags:not affectedFault Conditions:Type Code Cause Recovery Method4 57 The AHL instruction failed to execute because the serialport is set to no handshaking.Either:• Change the Control Line setting of the serial port.• Delete the AHL instruction.Execution:Condition Relay Ladder Action Structured Text Actionprescan The rung-condition-out is set to false. No action taken.rung-condition-in is false The rung-condition-out is set to false. narung-condition-in is trueThe instruction executes when rung-condition-intoggles from cleared to set.The rung-condition-out is set to true.naEnableIn is set na EnableIn is always set.The instruction executes.instruction executionThe instruction obtains the control line status and turns on or off DTR and RTS signals.The .EN bit is set.The remaining status bits, except .UL, are cleared.The instruction attempts to enter the ASCII queue.postscan The rung-condition-out is set to false. No action taken.Publication 1756-RM003I-EN-P - January 2007