Rockwell Automation T8314 Trusted Fibre TR/TX Unit - Manual (Page 8)

Trusted
TM
Fibre TX RX Unit T8314
Issue 10 Sep 08 PD-T8314 8
Figure 3 below shows the configuration of the Unit within a Trusted TM System using a remote Expander
Chassis.
Figure 3 Trusted TM Fibre TX/RX Unit Configuration
Six Units and six fibres are required for each remote link with three located at each end. A dual 24V dc
power philosophy is employed allowing the user to supply each Unit with dual power feeds.
Individual Units require no configuration prior to installation within a remote communications link. Each
Unit operates in a stand-alone mode allowing replacement without interrupting the operation of the
Trusted
TM System.
There are no diagnostics available, but the quality of communications may be checked by using the
Expander Interface and Processor diagnostics via the application program.
Note: Data is transmitted along the dual fibre-optic link at a rate of 250MHz. Signal skew will take
place but it must not exceed 80ns, which equates to a cable length difference of 15 metres.
This requires that synchronisation must take place at the start and end of each transmission.
Skew not exceeding 80ns can be guaranteed for distances up to 2km. For distances greater
than 2km, cable routes must be surveyed to ensure that the propagation time difference
between the shortest and longest distance of the three links is less than 80ns.