QCM : Central Alarm System Architecture and Communication — 9 questions

Explication

A well-designed system architecture that uses reliable communication protocols and effective polling mechanisms ensures that detectors report their status promptly, enabling timely alarm detection and response. This direct cause-effect relationship means that the architecture's quality directly impacts the system's effectiveness in detecting alarms.

Explication

The detector configuration table is stored in RAM as an array of 'Detector_t' structures, which can be modified during system operation to update detector parameters such as description, zone, or enabled status. Direct memory modifications allow real-time configuration changes, making option 0 correct. Rewriting firmware (option 1) is unnecessary and inefficient for runtime updates. Reloading from non-volatile memory (option 2) is possible but less efficient than in-memory modification for immediate changes. Sending commands over UART (option 3) is used for remote configuration, but the core in-memory data structure must also be updated to reflect changes; hence, modifying the table directly is the primary method of applying updates during operation.

Explication

The system restores detector configurations by reading the stored data from EEPROM, which contains a header with a magic number for validation. If the header's magic number matches, it proceeds to load the detector records, ensuring persistent configuration data is correctly restored after power cycles.

Explication

The RS485 protocol frame format explicitly starts with a header byte 0xAA, followed by the target address, command code, data length, data bytes, and a CRC for error detection, as described in the protocol details. The other options do not match the specified frame structure in the protocol.

Explication

The polling engine actively and periodically interrogates detectors to update their status, functioning proactively. Alarm handling, on the other hand, responds reactively when a detector has triggered an alarm, managing the alarm display and outputs. Thus, they serve different roles in the system.

Explication

The display LCD management functions are designed to update the LCD screen with current system status, including alarms, faults, and normal operation information, providing real-time visual feedback to the user.

Explication

EEPROM (Electrically Erasable Programmable Read-Only Memory) is a non-volatile memory used in the system to store configuration data persistently. This allows the system to retain settings and detector configurations even when powered off, ensuring reliable operation after restarts or power failures.

Explication

The UART configuration interface is typically set up during initial system installation to allow configuration and adjustments before the system becomes operational. This setup phase is when the system's hardware and software parameters are configured, including detector settings and network parameters, making it the correct time for establishing the UART interface for configuration.

Explication

Edsger Dijkstra is widely credited with advocating structured programming principles, which include the use of main program loops as a core control structure. His work laid the foundation for organized, readable, and maintainable code in procedural programming, establishing the concept of a main program loop as a standard pattern.