Digital Bus Reliability; Foundation Fieldbus; Profibus Dp-V0 And Dp-V1, Class 1 Masters; Hart Communications - GE Mark VIe Instruction Manual

8 Digital Bus Reliability

In addition to the variety of classic Mark VIe I/O modules, additional I/O modules are available for digital busses such as
F Fieldbus™, PROFIBUS
OUNDATION
modules consisting of a local processor that communicates on the IONET to switches and then to the controllers. Similarly,
they share a common ControlST* software suite with ToolboxST* configuration and diagnostic tools. It is beyond the scope
of this paper to review the redundancy options for each specific digital bus. However, some basic principles are provided for
reference.
8.1 F
OUNDATION
For reliability, two linking devices (I/O modules) can be connected with a RS-232C null modem cable to form one logical
linking device (a redundant set) in a primary / secondary configuration. Both linking devices are connected to the same H1
field devices and IONET. If the primary device were to fail, the secondary device would provide a backup. The original
primary could then be replaced and automatically reconfigured to match the new primary device.
For a typical application with redundant controllers, there is a primary controller (the designated controller) and a secondary
controller. Therefore, the primary linking device is the one connected to the primary controller. Less common are applications
with a single controller and redundant linking devices. In this scenario, the first linking device to be powered becomes the
primary.

8.2 PROFIBUS DP-V0 and DP-V1, Class 1 Masters

The I/O module can be configured for three types of redundancy:
• One I/O module with one I/O network
• One I/O module with dual I/O networks
• HotBackup I/O modules with dual I/O networks
The active master communicates with the slaves while the backup master is in standby mode. The backup is ready to
automatically switchover in less than 200 ms if any of the following conditions occur:
• All master/slave communication is lost
• Master/controller communication is lost on both I/O
• The master is powered down

8.3 HART Communications

Highway Addressable Remote Transducer (HART) communications provide diagnostics and remote communications to smart
field devices with standard 4-20 mA wiring. Each I/O module can communicate with dual redundant IONET switches.

8.4 CANopen Communications

The protocol specifications are developed and maintained by the Controller Area Network (CAN) in Automation standards
organization comprising. Each I/O module can communicate with dual redundant IONET switch.
Instruction Guide
® , HART ® , and CANopen
Fieldbus
Public Information
® . These modules share a common design with other I/O
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