Logix5000 Controllers General Instructions - SLAC Confluence

ASCII Serial Port Instructions (ABL, ACB, ACL, AHL, ARD, ARL, AWA, AWT) 5934. To trigger a subsequent action when the instruction is done,examine the EM bit.Arithmetic Status Flags:Fault Conditions:not affectednoneExecution: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 true The instruction executes when rung-condition-intoggles from cleared to set.naThe rung-condition-out is set to true.EnableIn is set na EnableIn is always set.instruction executionThe instruction executes.The instruction removes the specified characters from the buffer and stores them in the destination.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.Example:Continuously test the buffer for a message from a MessageViewterminal. Since each message ends in a carriage return ($r), thecarriage return is configured as the termination character in theController Properties dialog box, User Protocol tab. When the ABLfinds a carriage return, its sets the FD bit.When the ABL instruction finds the carriage return (MV_line.FD isset), the controller has received a complete message. The ARLinstruction removes the characters from the buffer, up to andincluding the carriage return, and places them in the DATA member ofthe MV_msg tag, which is a string.Publication 1756-RM003I-EN-P - January 2007