DVP-ES3 Series Programming Manual 9. The PLC operation flag SM400-SM403 SM400: The flag is always ON when CPU runs. _2 SM401: The flag is always OFF when CPU runs. SM402: The flag is ON only at the first scan. The pulse width equals one scan time. You can use this contact for the initial value setting. SM403: The flag is OFF only at the first scan. That is, the negative pulse is generated the moment the PLC runs. The PLC runs. SM400 SM401 SM402 SM403 Scan time 10. The initial clock pulse SM404 ， SM405 ， SM406 ， SM407 The PLC provides seven types of clock pulses. When the PLC is powered on, the seven types of clock pulses act automatically.
The clock pulses are illustrated in the following graphs. 2-86 Device Function SM404 10 millisecond clock pulse during which the pulse is ON for 5 milliseconds and then is OFF for 5 milliseconds SM405 100 millisecond clock pulse during which the pulse is ON for 50 milliseconds and then is OFF for 50 milliseconds SM406 200 millisecond clock pulse during which the pulse is ON for 100 milliseconds and then is OFF for 100 milliseconds SM407 One second clock pulse during which the pulse is ON for 500 milliseconds and then is OFF for 500 milliseconds