External trigger input

Fig.141: Digital output with external trigger and specification of pulse length and trigger delay

When using the digital input as a trigger pulse, this must first be configured as "Trigger input" in the CoE (see DOX Features).

In turn, "Output" and additionally "Input trigger enable" must be activated first in order to enable the trigger function.

Two different cases of the output of a pulse by trigger input are shown in the fig. Digital output with external trigger and preset pulse length and trigger delay:

Case 1:

• "Output" and "Input trigger enable" are already activated at T1 and the external trigger event is detected.
• "Output active" is set immediately, since "Trigger delay" has the value 0.
• After the "Impulse Length" T3 - T1 or if "Output" is deleted, "Output active" is likewise reset.

Case 2:

• "Output" and "Input trigger enable" are already activated at T4 and the external trigger event is detected.
• "Output active" is set for the duration of "Impulse Length" T6 - T5 on expiry of the time "Trigger delay".
• The resetting of "Output" at time T7 has no effect on the output, since the output time has already expired.

4 cases can be distinguished in the combination of the PDO and CoE values:

1. "PDO: Trigger delay" = 0, "CoE: Trigger delay" = 0
   -> no delay of the digital input
2. "PDO: Trigger delay" > 0, "CoE: Trigger delay" = 0
   -> delay of the digital input specified by the PDO value
3. "PDO: Trigger delay" > 0, "CoE: Trigger delay" > 0
   -> delay of the digital input specified by the PDO value, but maximally for the time configured in the CoE
4. "PDO: Trigger delay" = 0, "CoE: Trigger delay" > 0
   -> no delay of the digital input

Limitation of process data Unlike in the case of "Impulse length", "Trigger delay" is not overwritten with the associated CoE value if the process data value is 0, but is left as 0.

Trigger function with active watchdog By means of the configuration of "Trigger input (Watchdog disabled)" in Index 0x8002:32 (Function for input), the trigger input can be kept active in the case of a bus error->Watchdog active and pulses can still be output.