Section 8 - Interfacing to DSPs

Abstract

This chapter focuses on the interfacing to digital signal processing (DSP) technology in the rapidly growing field of mixed-signal processing. More highly integrated DSP products (such as the ADSP–21ESP202) have been introduced that contain on-chip analog-to-digital converters (ADCs), digital-to-analog converters (DACs), and the DSP, thereby eliminating most component level interface problems. Standalone ADCs and DACs are now available with interfaces especially designed for DSP chips, thereby minimizing or eliminating external interface support or glue logic. High performance sigma–delta ADCs and DACs are currently available in the same package (called a codec or COder/DECcoder) such as the AD73311 and AD73322. These products are also designed to fulfill minimum glue logic when interfacing to the most common DSP chips. This section discusses the various data transfer and timing issues associated with the various interfaces. Interfacing an ADC or a DAC to a fast DSP parallel requires an understanding of how the DSP processor reads data from a memory-mapped peripheral (the ADC) and how the DSP processor writes data to a memory-mapped peripheral (the DAC). It should be noted that the same concepts presented here regarding ADCs and DACs apply equally when reading and writing from/to external memory.