Appliance Design - October 2008 - (Page 33)

ELECTRONICS efficient power Fig. 1. STM32’s failsafe clock circuitry and dual watchdog system. be done periodically. If the application is systematically powered up before being used for a relatively short period, the tests done after the boot can be considered as periodic. On the other hand, if the application remains powered, the tests must be repeated during run-time also, and things become even more complicated: the RAM test must be transparent since it applies to memory cells being used by the application software. The principle of operation is presented in Fig. 2. A different set of C functions is provided for run-time tests. They have to be executed inside the highest priority interrupt routine, and several options are provided to avoid consuming too much CPU load or deteriorate the real-time responsiveness. The algorithm can be selected, either March C- or March X, which is slightly faster for a limited loss in terms of coverage. The number of memory cells being tested at once can also be parameterized in a header file, so that the duration of the interrupt routine can be finely adjusted down to few microseconds. This example shows how beneficial such a firmware library can be, as regarding development time. Similarly, some tests must be developed in assembly (typically the CPU tests - the C language hardly allows dealing directly with the core registers and flags); the assembly optimized routines provided with the library prevents the customer from having to learn the Cortex-M3 instruction set. Besides these individual tests, the self-diagnostic firmware also provides a reference Class B software framework when starting a new project, including workspaces for development tools, modified vector tables, and custom linker script files for handling Class A and Class B variables. Executed right after the reset vector fetch, a boot sequence implements all required tests before the application start (CPU, Watchdog, clock monitoring, RAM and FLASH tests), and can be reused as is. Once completed, this safe boot returns to the compiler’s C start-up entry point, so that all initial tests are completely transparent from the development tool’s point of view (RAM is verified before the automatic data initialization). The program sequence itself is monitored using a counter method, to verify that all tests are executed. Fig. 3 shows the principle of operation, based on inverse redundant variable storage and landmarking with prime numbers. Unexpected counter values or non-consistent redundant values at the end of the sequence will indicate an error and Rosenberg EC fans outperform the competition with quiet power and efficiency. Our axial designs deliver airflow up to 16,900 cfm. Our backward curved fans provide up to six inches of steady static pressure. Both operate 15-20% more efficient than traditional AC fans with VFD. They’re ideal for main-secondary or pressure control, and RS485 networks. Put the power of Rosenberg EC fans to work for you. Call: (704) 893-0883 • Fax: (704) 882-0755 sales@rosenbergusa.com • www.rosenbergusa.com Representatives Wanted applianceDESIGN October 2008 33 www.applianceDESIGN.com http://www.rosenbergusa.com http://www.rosenbergusa.com http://www.applianceDESIGN.com

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Appliance Design - October 2008 Contents Editorial Shipments/Forecasts News Watch Prototyping - Materials Play the Part Prototyping - Mix & Match Motors Electronics Coatings Design Marts Association Report: AHRI Advertiser's Index

Appliance Design - October 2008

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