How To Use Auto Online With The CP1L-EL/EM PLC

To provide an easy direct Ethernet online connection to the CP1E-EL/EM CPU Unit. 
Using CX-Programmer (Ver. 9.40 or higher), a CP1L-EL/EM can connect via Ethernet with an Auto-IP function. CX-Programmer's online connection command can be executed without any IP setting in the computer when the PLC is physically connected with the computer directly or via a hub. The Auto-IP (Auto Online/CP1E-Ethernet Online) function also facilitates connections to a CP1L-EL/EM with an unknown IP address.

The CP1L-Ethernet Online command will automatically detect a connected CP1L-EL/EM CPU and the transfer and online communication functions will occur.


However, there are conditions in which the CP1L-Ethernet Online feature does not function properly due to variations in network adapter configurations.


To correct this problem, use the DirectEthernetUtility (Direct Connection Utility) installed with CX-One.

First of all make sure that you selected the correct network adapter. e.g. the adapter where the PLC is connected to. A PC can have multiple adapters. 


The Direct Connection Utility must be enabled to use the Auto-IP (CP1L-Ethernet Online) function. In some cases, it could already be enabled but no connection is achieved. It is then necessary to disable and re-enable the Direct Connection Utility before attempting the Auto-IP function. The Direct Connection Utility functionality can be verified via the commandline (cmd.exe utility) using the ipconfig command. Look for the presence of an additional IPv4 Address of 169.254.XXX.XXX. When this is present, CX-Programmer can 'find' the CP1L-EL/EM unit and a connection can be established.

For example, if the network adapter (connected to the CP1L-EL/EM) is disabled at the moment of enabling the direct connection utility, the IPv4 function is not achieved properly when the network adapter is later enabled. In other words, the network adapter must be enabled and configured at the moment the direct connect utility is enabled. In this case, the additional IPv4 address of 169.254.XXX.XXX will be set properly and the Auto-ip connection can be established.

*NOTE: You must click OK to make the changes take affect.


  • No additional IPv4 Address Present on the adapter used for Ethernet communications to the CP1L-EL/EM (problematic):

  • An additional IPv4 address (169.254.XXX.XXX) is present on the adapter used for Ethernet communications to the CP1L-EL/EM (ready for auto-online):

Alternatively, use the file-new method in CX-Programmer to achieve an Ethernet connection to the PLC. However, you must know the first three octets for the CP1L-EL/EM IP address and your PC/PLC must be on that same network e.g. 192.168.250.XXX. The IP address of the CP1L-EL/EM may be obtained with the Direct Connection Utility by clicking "Confirm the network connection status". Additionally, the default IP address of the CP1L-EL/EM is 


The Auto Online functionality of CX-Programmer is typically a fast and easy method for establishing an online connection to a PLC. Due to various PC network adapter configurations, this feature may require additional steps before an online connection is achieved.

  • The above images were provided from the following software version: CX-One v4.24
  • See SYSMAC CP Series CP1L-EL/EM CPU Unit Operation Manual (Cat. No. W516) for more information