Rockwell Automation T8xxx Trusted Communications Interface - Manual (Page 12)

Trusted
TM
Communication Interface T8151B
Issue 21 Apr 10 PD-T8151B 12
1.3. Overview
The Trusted TM Communication Interface provides the Trusted TM System with an intelligent
communications interface, acting as a relay between the Processor, other Trusted TM Systems, the
Engineering Workstation and third-party equipment.
1.3.1. Hardware
The module has a Motorola Power PC processor. Bootstrap software is stored on EPROM.
Operational firmware is stored in flash memory and may be upgraded via the front panel port.
The Trusted TM Operating System is used on both the TMR Processor and Communication Interface.
The real time kernel is a high speed, high functionality kernel made for fault-tolerant distributed
systems. The kernel provides basic services (such as memory management) and interference free
software environments.
A module watchdog monitors processor operation and the power supply unit output voltages.
The module is supplied with a dual redundant +24V dc power feed from the chassis backplane. An
onboard power supply unit (PSU) provides voltage conversion, supply conditioning and protection.
The Trusted TM Communication Interface communicates with the Trusted TM TMR Processor via the
triplicated Inter-Module Bus. When polled by the Trusted TM TMR Processor, the module’s bus
interface votes the data (2-out-of-3) from the Inter-Module Bus and transmits back its reply via all three
Inter-Module Bus channels. The remainder of the communications interface is simplex.
All communications transceivers are isolated electrically from each other and the module and have
additional transient protection measures.
The module internal supplies are isolated from the dual 24Vdc feeds.
1.3.2. Communications
Ethernet MAC address configuration is held by the Communication Interface as part of its configuration
information. Other information regarding port and protocol configuration is obtained from the TMR
Processor, as part of the system INI configuration.
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
TM 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.
All changes to communications interface INI parameters may be loaded online and will take immediate
effect; the communications interface disconnects all communications and restarts. Communications is
also restarted on an application online update and is shut down when the application is stopped.