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A New Way to Get the Bumps out of Data Transfer
Reflective Memory Technology synchronizes in one sweep
Al Presher, Contributing Editor -- Design News, August 17, 2009
GE Fanuc Intelligent Platforms has announced a scalable, high-availability solution for its PACSystems® RX3i controller. The new system uses reflective memory technology (RMX) to implement multi-domain functionality at transfer speeds up to 20 times faster than 100 MHz Ethernet.
“Unique aspects of this solution are the use of very high-speed reflective memory and the amount of data (up to two Mbytes) that can be synchronized on one sweep,” says Bill Black, product manager for controllers at GE Fanuc. “The advantage is that all data is synchronized in one sweep, versus multiple sweeps, and offers a truly 'bumpless' transfer of control.”
A typical base sweep time for 8k of discrete I/O, 1k of analog I/O and 8k registers is 5.16 msec. “Some systems on the market are limited by the data sent as primary I/O and, once that limit is reached, secondary I/O can be synchronized, but there may be no guarantee that the transfer will be bumpless,” says Black.
Synchronization between controllers is done using an RMX module that goes into each controller which seamlessly synchronizes the data. Users can also set up a redundant sync link between separate modules to achieve true redundancy. Reflective memory offers a sync link speed of 2.12 Gbyte/sec and can connect redundant controllers over distances up to 300m using fiber-optic technology.
Data is synchronized twice per scan, at the beginning and end of the scan.
Black says a key improvement is easy to use software.
When the user creates a tag to be shared, the user simply selects an option to “share data” from a drop-down menu.
Click for full-size diagram
