Logix5000 Controllers General Instructions - SLAC Confluence

576 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 indicates that the instruction found the termination character or characters..POS DINT The position determines the number of characters in the buffer, up to and including the firstset of termination characters. The instruction only returns this number after it finds thetermination character or characters..ERROR DINT The error contains a hexadecimal value that identifies the cause of an error.DescriptionThe ABL instruction searches the buffer for the first set of terminationcharacters. If the instruction finds the termination characters, it:• sets the .FD bit• counts the characters in the buffer up to and including the firstset of termination charactersThe Controller Properties dialog box, User Protocol tab, defines theASCII characters that the instruction considers as the terminationcharacters.To program the ABL instruction, follow these guidelines:1. Configure the serial port of the controller for user mode anddefine the characters that serve as the termination characters.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.Arithmetic Status Flags:Fault Conditions:not affectednonePublication 1756-RM003I-EN-P - January 2007