Controller Architecture 9
Chapter 1 Theory of Operation
spare I⁄O modules. Consequently, both the active module and the hot-spare module
receive the same information from the field termination wiring.
A triplicated I⁄O bus transfers data at 2 megabits per second between the I⁄O
modules and the MP. The I⁄O bus is carried baseplate-to-baseplate and can be
extended to multiple columns of I⁄O modules. Each channel of the I⁄O bus runs
between one MP and the corresponding channel on the I⁄O module. The I⁄O bus
extends between DIN rails using a set of three I⁄O bus cables.
Logic power for the modules on each DIN rail is distributed using two independent
power rails. Each module along the DIN rail draws power from both power rails
through redundant DC-DC power converters. Each channel is powered
independently from these redundant power sources.
Controller Communications
The controller can communicate directly to TriStation and other devices through
the Main Processor Module and the Communication Module.
Main Processor Module
Each MP can provide direct TriStation and Modbus communication. Each MP
provides:
• One Tristation (Ethernet) port for downloading an application to the
controller and uploading diagnostic information.
• One Modbus RS-232/RS-485 serial port which acts as a slave while an
external host computer is the master. Typically, a distributed control system
(DCS) monitors—and optionally updates—the controller data directly
though an MP.
Communication Module
The Communication Module (CM) provides an optional, three-to-one interface to
the MPs that supports various protocols for communication with external hosts. A
single controller supports up to two CMs on one CM Baseplate. Each CM operates
independently. Two CMs can provide redundant communication connections or
independent communication ports.
To Next Page
Loading...