ALTUS Nexto Series User Manual

6. REDUNDANCY WITH NX3030 CPU
IF fbRedundancyManagement.m_fbDiagnosticsLocal.eRedState = REDUNDANCY_STATE.
ACTIVE THEN
SpecialVariablesRedundantPrg();
END_IF;
NonSkippedPrg();
IF fbRedundancyManagement.m_fbDiagnosticsLocal.eRedState = REDUNDANCY_STATE.
ACTIVE THEN
ActivePrg();
END_IF;
END_IF;
MainPrg call two POUs from the program type, called NonSkippedPrg and ActivePrg. NonSkippedPrg is always called,
as it’s executed in both CPUs. On the other hand, ActivePrg is only called when the “RedDgnLoc.sGeneral.Diag.eRedState =
Active” condition is true, in other words, when the CPU is in active state.
However, the NonSkippedPrg program is executed in both CPUs (PLCA and PLCB) independent on the redundancy state
of this CPU. On the other hand, the ActivePrg is executed only in the active CPU.
Opposite to the MainPrg, which must not be modified, the user may modify the NonSkippedPrg and ActivePrg programs.
Initially, when the redundant project is created from the Redundancy Template, these two programs are created “empty”, but
after that the user may insert his code.
ATTENTION
When the OPC option is enabled when creating the project, the NonSkippedPrg program is
not created empty. For more information, refer to the OPC DA Communication Use with
Redundant Projects section.
6.3.3.4. ActivePrg Program
The main goal of this program, which is executed only in the active CPU, is to control the final user process.
This program normally acts on the redundant variables, among which the direct representation variables are found %I and
%Q associated to the remote I/O system. For further information see the section Redundant CPU Programming - MainTask
Configuration - ActivePrg Program.
ATTENTION
The compilation being successful or not, MasterTool informs the calculated looseness and
the redundancy overhead predicted on the message window.
6.3.3.5. NonSkippedPrg Program
This program is executed in both CPUs (PLCA and PLCB) independent on the redundancy state. It’s typically used for
functions such as:
To organize non-redundant diagnostics to report to a SCADA system.
To receive and execute non-redundant commands from a SCADA system.
To manage switchover conditions normally not automatically contemplated by the redundant CPU, that can vary from
user to user. E.g. a user will be able to execute a switchover to the Reserve CPU if the Active CPU isn’t communicating
with the SCADA system, while another user may not want a switchover on this situation.
To enable or disable I/O drivers according to the redundancy state, e.g. disable a Modbus RS-485 master in the Inactive
CPU.
To detect failures in I/O drivers in an inactive CPU, in order to avoid obscure failures. Some I/O drivers don’t include
such failures automatically detection, while others, such as the PROFIBUS, does it automatically.
Other activities which, for some reason, need to be executed either in the Active CPU and the Reserve CPU.
For further information see Redundant CPU Programming - MainTask Configuration - NonSkippedPrg Program section.
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ALTUS Nexto Series Specifications

General

Brand	ALTUS
Model	Nexto Series
Category	Computer Hardware
Language	English