Here are a few potential questions related to the error described:

1. Can you describe what is meant by "abnormal communication"?
2. What is the purpose of PLC1-M7028-PLC1?
3. How would one go about checking the communication line machine code
The solution for the communication enable error between the front-end PLC1-M7028-PLC1 and PLC2 is to check the communication line for any potential issues such as physical damage or electromagnetic interference. It