Applies To:
  • CitectSCADA 5.xx, 6.xx
  • CitectHMI 5.xx, 6.xx

What is the optimal Citect communication setup for the S7 driver?

Do I configure Citect to use 1 port per I/O Device, or do I configure Citect to use 1 port for multiple I/O Devices?


Changes have been made to the S7 driver to reduce response time from the PLC and hence increase performance for large projects using multiple S7 PLCs.

1. If your Citect I/O Server is communicating to multiple Siemens S7 PLCs, then it is recommended that you configure your communication setup to use 1 port per I/O Device. This means that you will need a unique VFD Name and Connection Name for each of your port/I/O Device pair.

2. With multiple S7 PLCs on the network, the S7 driver will take longer to initialise and bring all of the I/O Devices online. Depending on the speed of your LAN network and the type of PLCs used (eg. S7-300 or S7-400), you can also adjust the

parameter [S7NT]ConnTimeout. This parameter is used to control how long to wait to bring an I/O Device online during initialisation.

3. For "small" projects, you can also configure your Citect I/O Server to use 1 port per I/O Device for optimal performance. You can also use multiple I/O Devices per port if you are using the older Siemens Softnet V3. The Siemens Softnet V6 only allows maximum of 10 connections or "channels" for external applications such as Citect. It can however support up to 64 Devices/PLC's to be shared among these 10 connections. If you require more than 64 PLC's on a single I/O Server, you can alternatively use the PSDIRECT driver

With PSDIRECT it is required that ALL IO devices are connected through one port.  PSDIRECT operates in a different way to many other drivers in this regard.