Triconex 3351S2 Controller Features

Each CM provides three RS-232/485 serial ports and two Ethernet ports. These ports support a variety of communication methods, protocols, and physical media types that enable the controller to communicate with:

 • External host computers 

 • Distributed control systems (DCS) 

 • Open networks 

 • Network printers 

 • Other Trident or Tricon V9 controllers

Input/Output Modules

The controller manages the data exchanged between the MP and the following I⁄O modules: 

 • Analog Input Module 

 • Analog Output Module 

 • Digital Input Module 

 •Digital Output Module 

 • Pulse Input Module 

 • Solid-State Relay Output Module

Analog Input Module

places the results into a table of values. Each input table is passed to its associated MP using the corresponding I⁄O bus. The input table in each MP is transferred to its neighbors across the TriBus. The middle value is selected by each MP and the input table in each MP is corrected accordingly. In TMR mode, the mid-value data is used by the application; in duplex mode, the average is used. Each AI Module is guaranteed to remain in calibration for the life of the controller; periodic manual calibration is not required. Special self-test circuitry is provided to detect and alarm all stuck-at and accuracy fault conditions in less than 500 milliseconds, typically. This safety feature allows unrestricted operation under a variety of multiple-fault scenarios.

Analog Output Modules

AO Module receives three tables of output values, one for each channel from the corresponding Main Processor. Each point on each channel has its own digital-to analog converter (DAC). One of the three channels is selected to drive the analog outputs. The outputs of the selected channel are continuously verified by I⁄O loop back inputs from each point, which are read by all three channels. If a fault occurs in the driving channel, the channel is declared faulty, is disabled, and a new channel is selected to drive the field device. The selection of the driving channel alternates among the channels so that all three channels are periodically tested. Each AO Module is guaranteed to remain in calibration for the life of the controller; periodic manual calibration is not required.

Digital Input Module

A Digital Input Module contains the circuitry for three identical channels (A, B, and C). Although the channels reside on the same module, they are completely isolated from each other and operate independently. Each channel conditions signals independently and provides optical isolation between the field and the controller. A fault on one channel cannot pass to another. In addition, each channel contains a proprietary ASIC which handles communication with its corresponding MP, and supports run-time diagnostics. Each of the three input channels measures the input signals from each point on the baseplate asynchronously, determines the respective states of the input signals, and places the values into input tables A, B, and C, respectively. Each input table is interrogated at regular intervals over the I⁄O bus by the I⁄O communication processor located on the corresponding MP. For example, MP A interrogates Input Table A over I⁄O Bus A. Special self-test circuitry is provided to detect and alarm all stuck-at and accuracy fault conditions in less than 500 milliseconds, typically. This safety feature allows unrestricted operation under a variety of multiple-fault scenarios. The input diagnostics are specifically designed to monitor devices which hold points in one state for long periods of time. The diagnostics ensure complete fault coverage of each input circuit even if the actual state of the input points never changes.

Digital Output Module

A DO Module contains the circuitry for three identical, isolated channels. Each channel includes a proprietary ASIC which receives its output table from the I⁄O communication processor on its corresponding main processor. All DO Modules use special quad output circuitry to vote on the individual output signals just before they are applied to the load. This voter circuitry is based on parallel-series paths which pass power if the drivers for channels A and B, or channels B and C, or channels A and C command them to close—in other words, 2-out-of-3 drivers are voted on. The quad output circuitry provides multiple redundancy for all critical signal paths, guaranteeing safety and maximum availability. A DO Module periodically executes an output voter diagnostic (OVD) routine on each point. This safety feature allows unrestricted operation under a variety of multiple-fault scenarios.

OVD detects and alarms two different types of faults: 

 • Points— all stuck-on and stuck-off points are detected in less than 500 milliseconds, typically. 

 • Switches—all stuck-on or stuck-off switches or their associated drive circuitry are detected.

During OVD execution, the commanded state of each point is momentarily reversed on one of the output drivers, one after another. Loop-back on the module allows each ASIC to read the output value for the point to determine whether a latent fault exists within the output circuit. The output signal transition is guaranteed to be less than 2 milliseconds (500 microseconds is typical) and is transparent to most field devices. For devices that cannot tolerate a signal transition of any length, OVD can be disabled. OVD is designed specifically to check outputs which typically remain in one state for long periods of time. The OVD strategy for a DO Module ensures full fault coverage of the output circuitry even if the commanded state of the points never changes.