The Internet of Things (IIoT) offers unprecedented possibilities for industries. Stay ahead with EcoStruxure™ Plant and Machine.Learn more
...with the EcoStruxure™ Facility Expert (formerly known as Facility Hero) app in hand! Discover how you can optimize your maintenance efforts today.Learn more
Access tailored services, 24/7 self-service and expert help. Anywhere, anytime, any project.Discover now
The story behind the Shedd Aquarium, a smart, sustainable facility that connects people to animals, with EcoStruxure™.Discover how
Welcome to the Schneider Electric Global Website×
Goals and Symptoms
To explain why ithe scan time for the Quantum HSBY is 4-5 times longer than it would normally be for a
standalone Quantum plc when a SCADA is connected using an NOE771xx.
Facts and Changes
This is a normal behaviour of the Hot Standby function.
Causes and Fixes
The reason for the long scan time delay is because the IEC Hot Standby function normally takes about
four to five times the scan time of a standalone controller. A delay in the SCADA's Modbus TCP/IP
communications update rate can also result in adding to the long scan time.
The use of 'Unlocated' variables in a 'Hot Standby' plc application can also result in a long scan time. The
reason is because 'Unlocated' variables are restricted to using only one master path. However, 'Located
Varaiables' are able to use up to four master paths. It is recommend that 'Located' variables be used in the
application whenever it is possible.
The scan time could also get extended if the defined 'IEC HotStandby Data Area' is too large or under sized.
The size of the 'IEC HotStandby Data Area' should be 25 percent more than the recommended size of the data area.
If Concept is used as the PLC programming software, the 'Analyze Program' function can be used to help determine
if the data area is too small.
Sign up for all the latest solutions, offers and best practices straight to your inbox.
We are excited that you have joined the group. You will receive your welcome email soon describing the program and what to expect in the upcoming weeks. Enjoy!