DMA transfer method for wide-range speed and frequency measurement

A frequency measurement method based on both pulse counting and time measurement during a constant sampling time is presented. The content of a free-running timer is transferred by a direct memory access (DMA) to a memory location after each rising edge of an input pulse, so the DMA transfer counter serves as a pulse counter. Several sources of measurement errors are discussed in detail. The DMA method is suitable for real-time speed control system with an integrated DMA controller.<
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