Rockwell Automation 1756-RMxx ControlLogix Enhanced Redundancy System User Manual - Manual (Page 21)

Rockwell Automation Publication 1756-UM535D-EN-P - November 2012 21
About Enhanced Redundancy Systems Chapter 1
HMI Blind Time Reduction on Ethernet During a Switchover
HMI Blind Time is the time during a switchover from primary to secondary,
when tag data from the controller is unavailable for reading or writing. HMI
Blind Time is associated with visualizing process operations from an HMI;
however, it is applicable to any software that uses tag data, such as data loggers,
alarming systems, or historians. Reducing HMI Blind Time is important to avoid
shutdowns.
Brief communication interruption occurs if the connection between RSLinx®
Enterprise software and the redundant chassis pair uses a path exclusively over an
EtherNet/IP network and a switchover occurs. After the switchover is complete,
communication resumes automatically.
The time between the communication (updating active data) interruption and
the restoration (resumes updates) is often referred to as ‘HMI Blind Time.’
Beginning with version 20.054, HMI Blind Time due to switchover has been
reduced.
HMI Blind Time is dependent on several system variables that determine this
length of time as follows:
• Quantity and types of tags on scan in RSLinx Enterprise software
• Client screen update rates
• Number of program and controller scope tags in the redundant controller
• Controller loading, which includes the following:
• Number of tasks and scan rates (assumes no continuous task)
• Memory usage
• Null task percentage available
• Network traffic
Based on testing with Windows Server 2003 software, ‘HMI Blind Time’ was
reduced between 40…80%. User results will vary based on the variables listed
above.
IMPORTANT RSLinx Enterprise software version 5.50.04 (CPR9 SR5) is required beginning with
version 20.054.
IMPORTANT RSLinx Enterprise software is part of FactoryTalk Services, which has been
releasing a series of Service Releases (SRs) that are backward compatible with
any CPR 9 products. The HMI Blind Time feature can be used by existing and
new users who are using FactoryTalk View version 5.0 (CPR9) or newer.