AH500 Programming Manual Symbol: S ： For internal use Bit Explanation: 1. When the value in the accumulative register turns from 1 to 0, the instruction FB_PN keeps the value 1 in the accumulative register for a scan cycle. After the second scan cycle is finished, the value in the accumulative register changes to 0. 2. The previous state of the contact is stored in the bit device S . Please do not use S repeatedly in the program. Otherwise, the wrong execution result will appear. 3. The instruction FB_PN only can be used in the function block. Example: Instruction: Operation: LD M0 Contact A of M0 is loaded. AND M1 Contact A of M1 is connected in series.
FB_PN D0.0 The circuit is falling edge-triggered. OUT Y0.0 The coil Y0.0 is driven. Timing diagram: M0 M1 One scan cycle One scan cycle Y0.0 5-24 Instruction code Operand Function FB PN _ S The circuit is falling edge-triggered. Device DX DY X Y M SM S T C HC D L PR S ● ● ● ● ● ● ● ● ● ● ●