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6. Redundancy with NX3030 CPU

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 NX5001 modules (PROFIBUS masters) in redundant configuration, configured in vital failure

mode.

 NX5000 modules (Ethernet) in configurations with NIC Teaming (redundancy managed by the

user).

Redundancy Overhead

A redundant application implies on an application processing time increase, when compared to the

necessary time for a non-redundant equivalent application.

This additional time happens due to cyclic synchronization services execution, described in the

Cyclic Synchronization Services through NETA and NETB section, and a smaller time for the

redundancy management (state machines, etc.). The total additional time due to redundancy

(redundancy overhead) is estimated by MasterTool, after the redundant CPU project compiling.

ATTENTION:

MasterTool calculated overhead consider an empty redundant variables forcing list.

It’s up to the user to define a cycle time for the MainTask which includes:

 The additional redundancy time estimated by MasterTool

 The necessary time to execute the main POUs (NonSkippedPrg and ActivePrg). This time

usually is measured after the project development (with the redundancy additional time off)

 Some MainTask cycle looseness, for other CPU tasks execution (operational system, I/O

PROFIBUS drivers, Modbus, etc.). This looseness percentage can vary according to the

requested performance from these other tasks. E.g. if the MODBUS communication with the

SCADA system needs to allocate too much processing to reach a satisfying performance, this

looseness must be increased

ATTENTION:

Depending on the memory alignment, the number of bytes used in the redundancy overhead calculus

might be higher than the total amount of bytes declared in the variables.

Redundant CPU Programming

Wizard for a New Redundant Project Creation

In order to create a new redundant project, the File/New Project command must be used and the

Standard MasterTool Project selected.

Initially, the user must inform the desired name for the project and the directory where he desire to

save it, as shown on Figure 6-15:

ALTUS Nexto NX3004 User Manual

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