Applies To:
  • CitectSCADA
  • CitectHMI
Summary:
I have 6 MelsecQ PLCs connected to a single Citect PC. Each PLC is connected to an Ethernet card on the Citect PC.

1. How many driver instances are created?
2. If one driver instance is created, will this affect performance of the communications.
 

Solution:
Only one instance of a driver is created regardless of the number of i/o devices present in the project.

In the case of the Melsecq driver, each NIC will be assigned a different channel, and the driver supports up to 32 channels.
Performance may be affected by having 6 NICs connected to individual PLCs, for example intermittent communications.
To prevent this, it could be a good idea to increase [Melsecq]MaxPending from its default in order to be able to service all 6 ports without being held up (e.g. set to at least 6).

 
Keywords:
MelsecQ, driver performance  

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