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ASCII Serial Port Instructions (ABL, ACB, ACL, AHL, ARD, ARL, AWA, AWT) Chapter 17 SERIAL_PORT_CONTROL Structure Mnemonic 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 AWT instruction sends the specified number of characters (Serial Port Control Length) of the Source tag to the device that is connected to the serial port of the controller. To program the AWT instruction, follow these guidelines: 1. Configure the serial port of the controller: If Your Application Then uses ARD or ARL instructions Select User mode does not use ARD or ARL instructions Select either System or User mode 2. This is a transitional instruction: • In relay ladder, toggle the rung-condition-in from cleared to set each time the instruction should execute. • In structured text, condition the instruction so that it only executes on a transition. 3. Each time the instruction executes, do you always send the same number of characters? If Then Yes In the Serial Port Control Length, enter the number of characters to send. No Before the instruction executes, move the LEN member of the Source tag to the LEN member of the Serial Port Control tag. Publication 1756-RM003K-EN-P - July 2008 Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com 595
