Chapter 4 System Operation; System Overview; Communications; Redundancy - Emerson PACSystems RX3i User Manual

User Manual
GFK-2911E

Chapter 4 System Operation

This chapter provides a System Overview and describes:
•

Communications

•

Redundancy

• I/O Scans
• Alarms
• Station Manager
4.1

System Overview

Communications
The EDS001 is a self-standing communication processor. During normal operation, it
handles asynchronous requests from its various DNP3 Masters and exchanges
corresponding data with the host RX3i CPU at designated portions of the CPU scan. It
performs all these tasks without burdening the CPU beyond the windows designated for
data exchange.
On power-up or reset will await the COMMREQ from the user application environment to
set its parameters and put it into operation. Once it receives its parameters, the module
scans the RX3i for data, based on its configuration. It detects and registers data changes
within its host PLC. It also services asynchronous DNP3 Master requests for polling (i.e.
reading of PLC data) and writing of data to PLC memory.
Because the module is self-standing, it polls the CPU during the CPU background scan
window for data, per its configuration. The module detects and records all corresponding
data changes internally. Whenever a master writes to it, the module must wait for the CPU
to allow it to write the corresponding information into the PLC memory during the same
window.
All Ethernet traffic is asynchronous to the RX3i CPU scanning operation, so the module can
service many different requests without burdening the CPU with processing them.
Redundancy
There are no restrictions which apply to an EDS001 when installed in a redundant RX3i CPU.
The polling of event and integrity data will occur as if it were in a simplex system.
The EDS001 can take advantage of the Redundant IP feature of a Redundant CPU system,
allowing two EDS001 modules in two racks to appear as one module.
System Operation
Chapter 4
Sep 2019
21