AD7622BSTZ datasheet(27/29 Pages) AD

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AD7622

Rev. 0 | Page 26 of 28

MICROPROCESSOR INTERFACING

The AD7622 is ideally suited for traditional dc measurement

applications supporting a microprocessor, and ac signal processing

applications interfacing to a digital signal processor. The

AD7622 is designed to interface with a parallel 8-bit or 16-bit

wide interface or with a general-purpose serial port or I/O ports

on a microcontroller. A variety of external buffers can be used

with the AD7622 to prevent digital noise from coupling into the

ADC. The SPI Interface (ADSP-219x) section illustrates the use

of the AD7622 with the ADSP-219x SPI-equipped DSP.

SPI Interface (ADSP-219x)

Figure 42 shows an interface diagram between the AD7622 and

an SPI-equipped DSP, the ADSP-219x. To accommodate the

slower speed of the DSP, the AD7622 acts as a slave device and

data must be read after conversion. This mode also allows the

daisy-chain feature. The convert command can be initiated in

response to an internal timer interrupt. The 16-bit output data

are read with three SPI byte access. The reading process can be

initiated in response to the end-of-conversion signal (BUSY

going low) using an interrupt line of the DSP. The serial peripheral

interface (SPI) on the ADSP-219x is configured for master

mode (MSTR) = 1, clock polarity bit (CPOL) = 0, clock phase

bit (CPHA) = 1, and the SPI interrupt enable (TIMOD) = 00 by

writing to the SPI control register (SPICLTx). It should be noted

that to meet all timing requirements, the SPI clock should be

limited to 17 Mbps, allowing it to read an ADC result in less

than 1 μs. When a higher sampling rate is desired, it is

recommended to use one of the parallel interface modes.

BUSY

SDOUT

SCLK

CNVST

AD7622

PFx

SPIxSEL (PFx)

MISOx

SCKx

PFx OR TFSx

ADSP-219x1

DVDD

MODE0

MODE1

EXT/INT

INVSCLK

1ADDITIONAL PINS OMITTED FOR CLARITY.

Figure 42. Interfacing the AD7622 to ADSP-219x

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