Software design considerations

Embedded software utilizes full variability programming language,, is provided by PES suppliers, and is typically transparent to the preparation of application software. Considerations that should be understood before proceeding with the application software development include the following  

Utility software typically utilizes either limited variability software or fixed programming languages. Use of utility software should adhere to the same criteria as embedded software. Utility software from third parties may be available and considered for use. Use of third-party utility software for applications program development, without testing and approval of the PES manufacturer of the utility software package, is not recommended. 

Limited variability languages that are mature and/or have been certified to accepted industry standards, such as lEC 61131-3 Programmable controllers - Part 3 Programming Languages), are preferred. 

Programming guidelines should be established to enforce consistent style among the design team. Implementation of a software quality plan may facilitate development of a consistent programming style. 

To avoid unnecessary complexity and features that make the behavior of the application logic difficult to predict, the following should be considered  

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The second design consideration is the dead time associated with the PWM control signals. The dead time is determined by the device turnoff time and snubber decay times. Catastrophic GTO failure would occur if both devices in one halfbridge were to conduct simultaneously. The PWM control software was modified to produce a conservative 15-/ts dead time. 

At the cost of more complex mathematics encountered by the software designer, the method offers to the cell designer a user-friendly device. The mean reason for this is the considerable reduction in time required to introduce a given problem. 

Any new hardware requirements and capabilities are examined with respect to their potential impact on the software systems. This evaluation should include all hardware considerations reviewed in the original software design. If it can be shown that the new system does not impact the software requirements, a simplified procedure may be used to implement the modification either at the design or coding phase. 

Course offerings can vary considerably among universities, so the student must consider the specialties of the prospective schools in relation to the field in which he or she is most interested. For example, the student may want to focus more on software design than on graphics design. Essential courses can include... 

The requirements for and design of the software for systems important to safety should exphdtly define all relations between input and output for each of the operating modes. The software design should be simple enough to permit consideration of all input combinations that represent all operating modes. 

Fig. 5 shows a schematic of the proposed framework s structure, showing the stepwise-proposed procedure, the inter-linking of the software tools used and the flow of data between them. The remainder of this section describes in details each step of the integrated framework and their role in the optimal design considerations. 

With plant that is controlled by computer, the HAZOP study needs to include consideration of the effects of aberrant computer behaviour and the team carrying out the study may need to be reinforced by the software designer plus an independent software engineer able to question the philosophy of the installed software program. A technique known as CHA-ZOP has been developed for such plant which also highlights the safety critical control items. 

An SDF is a repository for a collection of material pertinent to the development or support of software. Contents typically include design considerations and constraints, design documentation and data, schedule, and status information, test requirements, test cases, test procedures, and test results. 

Safety-related equipment, safeguards, and possible alternative approaches (e.g., monitoring, interlocks, system redundancy, hardware or software fail-operational/fail-safe design considerations, subsystem protection, fire detection/suppression systems, personal protective equipment, ventilation, and noise or radiation attenuation)... 

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