ICS TRIPLEX TC-305-01-5M0 Trusted Communications Cables

The Trusted® TMR 24 Vdc Digital Input module interfaces to 40 field input

devices. Fault tolerance is achieved through a Triple Modular Redundant

(TMR) architecture within the module for each of the 40 input channels.

Each field input is triplicated and the input voltage is measured using a

sigma-delta input circuit. The resulting field voltage measurement is

compared to user configurable threshold voltages to determine the reported

field input state. When a line-monitoring device is installed at the field switch,

the module can detect open and short circuit field cables. Line monitoring

functions are independently configured for each input channel.

The triplicated voltage measurement, coupled with onboard diagnostic testing,

provides comprehensive fault detection and tolerance.

The module provides onboard Sequence of Events (SOE) reporting with a

resolution of 1 ms. A change of state triggers an SOE entry. States are

determined by voltage thresholds that can be configured on a per channel

basis.

Data is transferred between the TMR Processor and the Communications Interfaces using a

common interface called the Network Variable Manager. When data is read from a Trusted

System, the data is obtained from the local copy maintained on the Communications

Interface, providing a fast response.

Data writes are more complicated. If a data write simply updated the local copy and was

then relayed to the processor, the other Communications Interfaces in the system would

carry different data. This may cause problems for redundant links.

To overcome this problem, when data is written to a Communications Interface, it is first

passed to the TMR Processor and the write is acknowledged immediately by the

Communications Interface (to avoid communications delays). The processor updates its own

database and then sends the data back to all Communications Interfaces so that they all

have the same data. This can take one or two application scans. This means that subsequent

reads will receive the old data immediately after the write, until the new data has been

distributed.