User Manual
Chapter 4
GFK-2849A
Oct 2019
System Operation
81
Figure 79
4.3.1
RX3i CPU Sweep
The RX3i CPU Sweep illustrated above is a repeating sequence that includes an input scan,
logic solution, and an output scan. The CPU input scan retrieves the latest input data
collected from the IEDs and buffered in the ECM850. After this, the input data is used by the
application logic to determine new output data. During the RX3i output scan, the CPU
writes the newly computed outputs to the ECM850, which in turn pushes this output data
immediately to the IEDs.
4.3.2
RX3i Input Scan
At the start of every input scan, the RX3i CPU sends a request to the ECM850 for its input
data. On receipt of this notification from CPU, the ECM850 unconditionally sends its latest
input data from the
IEDs to the CPU. The age of the data in the ECM850’s input data buffer
will depend on the configuration of each IED, as described in Chapter 3. By default, each IED
is polled by the ECM850 for input data every second (although this period is configurable).
Alternately, the IEDs can be configured to report certain data immediately on change, as
described in section 3.4.1 Report Control Block (RCB) overview Except in the latter case, the
updating of IED input data in the RX3i is essentially asynchronous to the CPU sweep.
4.3.3
RX3i Output Scan
The CPU sends IED output data to the ECM850 during every output scan. At the end of the
output scan, the ECM850 sends the latest output data unconditionally to IEDs through its
