A first restraint in development of application is that specification, design and activities of coding will be geographically far-away from each other. In sequence to follow the development and validate that the transitions between the phases are possible, a minimum of formal documentation will be necessary. A second restraint is that one system I&C of plant may control some components which have been acquired individually. The strategy to address this issue is explained in the PCDH.
The lifecycle planned addresses the core application software development of every PLC in a whole system of plant system I&C. Some systems of plant system I&C will be very large and will execute some high level functions. The one plant system I& development C can be crashed in some life cycles. Generally, a developer of PLC is in charge of one (or some) high-level function, spread on one or some PLCs. It is recommended that one life-cycle is involves one high level function activity, and consequently one PLC developer activity. The life cycle is nothing more than the special steps pursued in a normal life cycle of software engineering. The only innovation here is in the adding of a stage of integrated validation testing.
As the design detailed of the plant system I&C will be finished as the software development initiates, a documents full set will be accessible, crashed in 9 deliverables as identified in the PCDH. These deliverables will comprise the architecture of I&C hardware, an analysis of functional, an Inputs/Outputs list, etc.
Software specifications are fully covered during the design phase of I&C. They will be mostly covered in the analysis of functional, but other inputs for example state machines and philosophy of control will also be applied.
Two phases in the Software Design are considered: a design of architectural and a design of detailed. The design of architectural will be also involved by the analysis of functional, as it will identify the major action blocks inside the core application. It is not necessary that the blocks of peripheral are defined, as they will all be built up base on templates or will be produced automatically. The design of detailed contains of defining how all the functions will be executed. The following information should be offered for each controller at this stage:
• The each programming block naming and numbering: FB,DB,OB,FC,
• The section of core application for full program structure of each OB.
• Any detailed network, hardware, configuration or project used.