- Flexibility
• All interfaces might be not accessible during integration and commissioning. The application should permit some signals to be required, or the missing interface partial simulation.
- Maintainability
• Adequate system information should be supplied.
• The application of PLC should be integrated a way that changes have only local impact.
- Ability to be tested
• PLC functions for unit testing should simple.
• The software of control systems should be tested separately from the system. The idea is to check the system of control when it is linked to a simulator rather than the system. The designer of plant system must identify beforehand which controllers must be tested together.
- Readability
• Every transformation of information should be simple to track.
The principle is to have a universal architecture for functions inside all the PLCs arranged on the project. According to the particular application of PLC, all the blocks might not be showed. For instance:
• A “Master Controller”, in the architecture of I&C will not have any hardware interface of Input/Output but will have many interfaces with other PLCs in the manufacturing system.
• Interfaces with fast controller will possibly be very extraordinary and may use the interface of CODAC, as Fast Controllers are operation EPICS and are accordingly linked to Channel Access.
Excluding for the core application of PLC, the structure internal of all other blocks will be typical for all PLCs organized on the project. Only the structure and volume of the data calculated in these blocks will be dissimilar. As far as possible, these blocks will be produced automatically, using the arrangement database as input. The interface of CODAC will be fully produced by the package of SDD. Additional production activities will be based on these structures. The regulation loops and state charts of the process will be realized. Only process programming should be establish here. The core application of PLC will implement the functions of control. Its functionality will be exaggerated by all the interfaces. All the treatment or programming not directly involving the process is carried out in the peripheral blocks such as, interfaces, system monitoring.
The core application of PLC will use the variables of configuration which is transferred by the Interface of CODAC as the key inputs from operation. Some variable of configuration for instances:
- requests ON/OFF
- requests OPEN/CLOSE,
- request HIGH VACUUM/ROUGHING/VENTING,
- Temperature set point
- Current set point,
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EPICS PLC
EPICS PLC