6. HX3040 Redundancy
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Redundant CPU General Features
Redundant data synchronization
At each MainTask cycle, CPUA and CPUB exchange diagnostics and commands.
The user has 128 redundant data bytes available within the redundant CPU
diagnostics. The synchronism occurs through the channels between the CPUs. This
way, a CPU knows the diagnostics and commands of the other.
Redundant variables
synchronization
At each MainTask cycle, the Active CPU copies redundant data to the Inactive CPU
through the synchronism channels. Non-redundant data are not synchronized.
Redundant forcing list
synchronization
Each MainTask cycle, the Active CPU copies the redundant forcing list to the Inactive
CPU through the synchronism channels. This list includes only forced redundant
variables, so CPUA and CPUB can have different non-redundant data groups forced,
as these forcing are not synchronized.
The DNP3 event queue is also synchronized in the procedure of the CPU, even
though it is not enabled by the user. Further information on Redundant Data
Synchronization.
Single project for CPUA and
CPUB
There is a single project for the CPUA and CPUB, generated by MasterTool. The
project is composed by the applicative project (executable code) and the archive
project (source code).
CPU identification
The CPUs are automatically identified as CPUA (position 2) or CPUB (position 3)
depending on the position in which they are inserted. This identification is not part of
the applicative project generated by MasterTool Xtorm. The CPU identification allows
the feature of supporting a single project for CPUA and CPUB.
Automatic synchronization of the
project
If the Active CPU project becomes different from the Inactive CPU, it will be copied
from the former to the later. This synchronization can take several MainTask cycles.
One must remember the project is comprised by the applicative project (executable
code) and the archive project (source code), both are synchronized.
Private IP addresses for CPUA
and CPUB
In order to obtain specific diagnostics of a CPU it is possible for the user to connect
to a specific CPU (A or B) using its private IP address, for instance. For that, the user
should use the Web interface or the MasterTool programming tool. It is only possible
to check the diagnostics associated to communication protocols in the active CPU.
Active IP
Name of a strategy that allows Ethernet clients connect to a server in the redundant
CPU using always the same IP address. This prevents the necessity of complex
scripts to change the IP address in case of switchovers caused by redundancy. The
Active IP address will always be associated to the NET(i) interface of the Active
CPU.
NIC Teaming
Name of a strategy that allows two CPU Ethernet interfaces to form a redundant pair
using the same IP address. Thus, it makes easier the building of redundant Ethernet
networks. Furthermore, there is no need for the clients (connected to a NIC Teaming
pair) to implement complex scripts in order to switch IP addresses.
Cyclic user task
Only one user task is allowed (MainTask). It is designed to be the primary task, with
the bigger part of the user logic.
Main POUs
At a redundant project creation, MasterTool automatically generates two empty
programs POUs, which must be filled by the user.
POUs associated to MainTask
- NonSkippedPrg: this program POU is executed in both CPUs (A and B), regardless
of the redundancy state (Active or Inactive). It is used for diagnostics and special
commands management.
- UserPrg: this program POU is executed only in the Active CPU It is designed for the
final user’s process control.
- StartPrg: this program POU is executed in both CPUs (A and B), only in the first
cycle of MainTask.
POUs associated to ProtTask:
- MainPrg: This POU calls other POUs and administrates them. It cannot be edited.
- AlarmPrg: This POU will be associated to the alarms, which are being used in the
user’s application. It cannot be edited.
-EngineeringPrg: As the AlarmPrg, it is also automatically created, except that it
deals with the Project engineering processes. It cannot be edited.
Table 6-1. Redundant CPU General Features
