Triconex 3351S2 Controller Features

To ensure the highest possible system integrity at all times, the Trident controller includes the following features:

• Provides Triple Modular Redundant (TMR) architecture, whereby each of three identical channels independently executes the application, and specialized hardware and software mechanisms vote all inputs and outputs. 

 • Withstands harsh industrial environments. 

 • Integrates the I⁄O module with the termination assembly. 

 • Enables field installation and repair to be done at the module level while the controller remains online without disturbing field wiring. 

 • Supports up to 14 I⁄O modules. (If the controller includes AO or PI Modules, up to 10 modules are supported.) 

 • Provides TriStation and Modbus communication directly from the Main Processor (MP) or from the Communication Module (CM). 

 • Executes applications developed and debugged using TriStation. 

 • Provides a dedicated co-processor which controls the input and output modules to reduce the workload of the MP. Each I⁄O module is supported by custom application-specific integrated circuits (ASICs), which scan inputs and perform diagnostics to detect hardware faults. Output module ASICs do the following:– Supply information for voting of output data.– Check I⁄O loop-back data from the output terminal for final validation of the output state.– Perform diagnostics to detect hardware and field-wiring problems. 

 • Provides integral online diagnostics with adaptive-repair capabilities. 

 • Allows normal maintenance while the controller is operating, without disturbing the controlled process. 

 • Supports hot-spare I⁄O modules for critical applications for which prompt service may not be possible. 

 • Provides integral support for redundant field and logic power sources.

Fault Tolerance

Fault tolerance, the most important capability of the controller, is the ability to detect transient and steady-state error conditions and take appropriate corrective action online. Fault tolerance provides an increase in safety and the availability of the controller and the process being controlled. The Trident controller provides fault tolerance through TMR architecture. 

The controller consists of three identical channels (except for the power modules which are dual-redundant). Each channel independently executes an application in parallel with the other two channels. Voting mechanisms qualify and verify all digital inputs and outputs from the field; analog inputs are subject to a mid-value selection process. 

 Because each channel is isolated from the others, no single-point failure in any channel can pass to another. If a hardware failure occurs in one channel, the faulty channel is overridden by the other channels. Repair consists of removing and replacing the failed module in the faulty channel while the controller is online and without process interruption. 

 Extensive diagnostics on each channel, module, and functional circuit immediately detect and report operational faults by means of indicators or alarms. All diagnostic fault information is accessible by the application and the operator. The operator can use the diagnostic information to modify control actions or direct maintenance procedures.

Controller Architecture

The controller features TMR architecture to ensure fault tolerance and error-free, uninterrupted control in the event of hard failures of components or transient faults from internal or external sources.

Each I⁄O module houses the circuitry for three independent channels. Each channel on the input modules reads the process data and passes that information to its respective MP. The three MPs communicate with each other using a proprietary, high-speed bus called the TriBus.

Once per scan, the MPs synchronize and communicate with their neighbors over the TriBus. The TriBus forwards copies of all analog and digital input data to each MP and compares output data from each MP. The MPs vote the input data, execute the application, and send outputs generated by the application to the output modules. In addition, the controller votes the output data on the output modules as close to the field as possible to detect and compensate for any errors that could occur between the TriBus voting and the final output driven to the field.

For each I⁄O module, the controller can support an optional hot-spare module. If present, the hot-spare takes control if a fault is detected on the primary module during operation. The hot-spare position is also used for the online hot repair of a faulty I⁄O module.

Main Processor Architecture

A controller contains three MPs. Each MP controls a separate channel and operates in parallel with the other two MPs. A dedicated I⁄O control processor on each MP manages the data exchanged between the MP and the I⁄O modules. A triplicated I⁄O bus, located on the baseplates, extends from one column of I⁄O modules to another column of I⁄O modules using I⁄O bus cables. As each input module is polled, the appropriate channel of the I⁄O bus transmits new input data to its MP. The input data is assembled into a table in the MP and is stored in memory for use in the voting process.