The actual outputs are set using the output word bits. Outputs – Building a PLC Program – Traffic Light If they are equal then move the output table word to the output channel and increment the pointers to the next step. We now compare the actual inputs after the mask with the input table word. On this step, we then determine if the pointers need to be changed for the other two. You will notice that the first three sequences are all the same. This is used to ignore the inputs that we do not want to see or may not know the status during the execution of the program. The table input pointer is compared to the last value +1 of the sequence running. You will see that since we have three different sequences running, there are three different reset rungs in parallel. It resets the pointers and moves the initial output setting to the output word. This section of the control will tell the PLC what to do when the unit is first powered on. This sets the minimum time between each step.Ĭontrol – Building a PLC Program – Traffic Light The program is all controlled by one on-delay timer. Inputs – Building a PLC Program – Traffic Light
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