Triconex 3351S2 Controller Features

 The individual input table in each MP is transferred to its neighboring MP over the TriBus. After this transfer, voting takes place. The TriBus uses a programmable device with direct memory access to synchronize, transmit, and compare data among the three MPs. If a disagreement occurs, the signal value found in two of three tables prevails, and the third table is corrected accordingly. One-time differences which result from sample timing variations are distinguished from a pattern of differing data. Each MP maintains data about necessary corrections in local memory. Any disparity is flagged and used at the end of the scan by the built-in fault analyzer routines to determine whether a fault exists on a particular module. 

 The MPs send corrected data to the application. The 32-bit MP executes the application in parallel with the neighboring MPs and generates a table of output values that are based on the table of input values according to user-defined rules.The I⁄O control processor on each MP manages the transmission of output data to the output modules by means of the I⁄O bus.

Using the table of output values, the I⁄O control processor generates smaller tables, each corresponding to an individual output module. Each small table is transmitted to the appropriate channel of the corresponding output module over the I⁄O bus. For example, MP A transmits the appropriate table to channel A of each output module over I⁄O bus A. The transmittal of output data has priority over the routine scanning of all I⁄O modules.

Each MP provides a 16-megabyte DRAM for the user-written application, sequence-of-events (SOE) and I⁄O data, diagnostics, and communication buffers. (For more information about SOE, see the Sequence of Events Recorder User's Manual.) The application is stored in flash EPROM and loaded in DRAM for execution. The MPs receive power from redundant 24 volts DC power sources. If an external power failure occurs, all critical retentive data is stored in NVRAM. A failure of one power source does not affect controller performance. If the controller loses power, the application and all critical data are retained indefinitely.

Bus and Power Distribution

The triplicated I⁄O bus, as shown on page 8, is carried baseplate-to-baseplate using Interconnect Assemblies, I⁄O Extender Modules, and I⁄O bus cables. The redundant logic power distribution system is carried using Interconnect Assemblies and I⁄O Extender modules.

serial links operating at 25 megabits per second. The TriBus synchronizes the MPs at the beginning of a scan. Then each MP sends its data to its upstream and downstream neighbors. The TriBus takes the following actions: 

 • Transfers input, diagnostic, and communication data 

 • Compares data and flags disagreements with the output of the previous scan and program memory

An important feature of the Trident controller architecture is the use of a single transmitter to send data to both the upstream and downstream MPs. This ensures that the same data is received by the upstream processor and the downstream processor.

Field signal distribution is local to each I⁄O baseplate. Each I⁄O module transfers signals to or from the field through its associated baseplate assembly. The two I⁄O module slots on the baseplate tie together as one logical slot. The right or left position holds the active I⁄O module and the other position holds the hot-spare I⁄O module. Each field connection on the baseplate extends to both active and hot-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.