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PSDIRECT driver for CitectSCADA
3. The data is already available when a client polls it and data is displayed immediately
without delay. For example popup screens open instantly with data from the cache.
4. The back-end polls raw blocks of data from the PLC. The front-end can then request
any data type from this one polled block. This results in substantial efficiencies when
you have many mixed data types in close address proximity. For example: Siemens
Instance DB’s (User Defined types) like the PID loop DB’s are very complicated
structures containing floats, words & bits. The CitectSCADA S7NT driver would
generate a poll for each data type whereas this driver would read the information in
one network poll block of bytes to be stored in the cache, the Front end driver then
processes a CitectSCADA Driver request for each data type from the same cached
data.
5. Communications can be configured and debugged outside CitectSCADA.
1.4
Advantages over the Siemens Softnet Solutions
This section refers to the Siemens Ethernet back-end.
To setup Siemens Simatic Net on a PC and to test the communication can be very tedious.
Multiple IO servers have to be used to communicate to more than 20 PLC effectively.
The PSDIRECT driver will take 5 minutes to install. The driver works with any standard 10MB,
100MB or 1GB Ethernet card. To date more than 50 PLCs on a single system have been
tested with one standard 100Mb card. Multiple Ethernet cards can be used to communicate
to PLCs, however there are no real performance or reliability gains. The driver works equally
well sharing CitectSCADA, Windows workgroups, & Siemens ISO thru 1 Ethernet card. A
good Ethernet switch handles different link speeds & network node isolation & redundancy.
The PLC’s are the bottlenecks & the total Ethernet bandwidth used by the Ethernet card is <
5% typically. This driver maximises the communication to all the PLC’s on you network by
implementing a multithreaded parallel polling strategy.
This driver supports up to 128 PLC’s on one Network. It has been proven on a system with
50 PLC’s & 80 000 IO.
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