Sure, here are some questions related to this error:

1. What is the function of the PLC Marker point photo request signal?
2. What does it mean when the PLC Marker point photo request signal timeout occurs?
3. What is D206 and what does it indicate
M138-CCD reads the PLC Marker point photo request signal timeout (D206=1) indicates that the marker point photo request did not receive a response from the PLC. This could be due to communication issues