AD7631BSTZ datasheet(30/32 Pages) AD

30 / 32 page

AD7631

Rev. A | Page 30 of 32

SCIN

SCCLK

START

TEN

123

BUSY

HW/SW = 0

INVSCLK = 0

CNVST

SCCS

t36

t35

t37

BIPOLAR

OB/2C

MODE[1:0] = 3

BIPOLAR = 0 OR 1

TEN = 0 OR 1

PD = 0

t33

t34

t31

Figure 47. Serial Configuration Port Timing

MICROPROCESSOR INTERFACING

The AD7631 is ideally suited for traditional dc measurement

applications supporting a microprocessor and ac signal processing

applications interfacing to a digital signal processor. The

AD7631 is designed to interface with a parallel 8-bit or 18-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 AD7631 to prevent digital noise from coupling into the ADC.

SPI Interface

The AD7631 is compatible with SPI and QSPI digital hosts and

DSPs, such as Blackfin® ADSP-BF53x and ADSP-218x/ADSP-219x.

Figure 48 shows an interface diagram between the AD7631 and

the SPI-equipped ADSP-219x. To accommodate the slower

speed of the DSP, the AD7631 acts as a slave device, and data must

be read after conversion. This mode also allows the daisy-chain

feature. The convert command could be initiated in response to

an internal timer interrupt.

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 SPI interrupt enable

(TIMOD) = 0 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,

use one of the parallel interface modes.

BUSY

SDOUT

SDCLK

CNVST

AD7631*

PFx

SPIxSEL (PFx)

MISOx

SCKx

PFx OR TFSx

ADSP-219x*

*ADDITIONAL PINS OMITTED FOR CLARITY.

DVDD

MODE[1:0]

EXT/INT

INVSCLK

Figure 48. Interfacing the AD7631 to SPI Interface

AD7631BSTZ Datasheet(PDF) 30 Page - Analog Devices

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