1. Check the hardware for EMS4 card, and check the port working state, nothing is abnormal.
2. Compare the difference betweet port 1 and port 2 as LPT can work normally in port1, found service type is different, EPL service is in the port1, but EPLAN is in the port2.
3. Change the service form EPLAN to EPL in the port2, it is normal for LPT option, and can be set.
LPT function is supported in EMS4 card as confirmed according to the documents, so we shold check whether the port have some issue or not. As the first port is OK and LPT can be enabled, so we compare this two ports configuration in order to find the difference. Fininally, we found that EPL service is configured in the Port 1 but EPLAN service configured in the port2. So we change the service type form EPLAN to EPL, then enable LPT option appears normally.
LPT function can be used for EPL service only confirmed by R&D