This application note explains how to interface parallel ADCs to ADSP-21365 SHARC® processors. The parallel ADC considered in this application note is the AD7865. The two schemes described in this application note to interface an AD7865 with an ADSP-21365 are the parallel port interface and the parallel data acquisition port (PDAP) interface. This application note also provides example code to demonstrate how the SHARC processor’s parallel port and PDAP can be programmed to receive data from an AD7865 in DMA mode.
The AD7865 is a fast, low-power, four-channel simultaneous sampling 14-bit A/D converter that operates from a single 5 V supply. The device contains a 2.4 µs successive approximation ADC, four track/hold amplifiers, 2.5 V reference, on-chip clock oscillator, signal conditioning circuitry, and a high-speed parallel interface. The input signals on four channels are sampled simultaneously. This preserves the relative phase information of the signals on the four analog inputs.
The device allows any subset of the four channels to be converted, maximizing the throughput rate on the selected sequence. The channels to be converted can be selected via hardware (channel select input pins) or via software (programming the channel select register).
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