可编程序控制器(西门子S7-200).ppt
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* Analog Inputs (AI) * The On-Delay Timer and Retentive On-Delay Timer instructions count time when the enabling input is ON. When the current value (Txxx) is greater than or equal to the preset time (PT), the timer bit is ON. Both the On-Delay Timer and the Retentive On-Delay Timer continue counting after the Preset is reached, and they stop counting at the maximum value of 32767. The Reset (R) instruction can be used to reset any timer. The Reset instruction performs the following operations: Timer Bit = OFF Timer Current = 0 * The Off-Delay Timer is used to delay turning an output OFF for a fixed period of time after the input turns OFF. When the enabling input turns ON, the timer bit turns ON immediately, and the current value is set to 0. When the input turns OFF, the timer counts until the elapsed time reaches the preset time. When the preset is reached, the timer bit turns OFF and the current value stops counting. If the input is OFF for a time shorter than the preset value, the timer bit remains ON. The TOF instruction must see an ON to OFF transition to begin counting. * The Count Down Counter counts down from the preset value on the rising edges of the Count Down (CD) input . When the current value is equal to zero, the counter bit (Cxxx) turns on. The counter resets the counter bit (Cxxx) and loads the current value with the preset value (PV) when the load input (LD) turns on. The Down Counter stops counting when it reaches zero. S7-200 A502 In STL, the CTD Load input is the top of stack, and the Count Down input is the value loaded in the second stack location. Inputs/Outputs Cxxx CU, CD, LD, R (LAD) CU, CD, R, LD (FBD) PV L A D L F B D S Cxxx CD LD PV CTD * In STL, the CTUD Reset input is the top of the stack value, the Count Down input is the value loaded in the second stack location, and the Count Up input is the value loaded in the third stack location. 222 224 221 226 使用线圈输出指令时,同一编号的继电器线圈在同一程序中使用两次以上,称为双线圈输出。双线圈输出容易引起误动作或逻辑混
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