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Data Sheet

AD7787

Rev. A | Page 17 of 20

Continuous Read Mode

Rather than write to the communications register each time a

conversion is complete to access the data, the AD7787 can be

placed in continuous read mode. By writing 00111100

(Channel AIN1) or 00111101 (Channel AIN2) to the

communications register, the user only needs to apply the

appropriate number of SCLK cycles to the ADC, and the 24-bit

word is automatically placed on the DOUT/RDY line when a

conversion is complete.

When DOUT/RDY goes low to indicate the end of a

conversion, sufficient SCLK cycles must be applied to the ADC,

and the data conversion is placed on the DOUT/RDY line.

When the conversion is read, DOUT/RDY returns high until

the next conversion is available. In this mode, the data can only

be read once. Also, the user must ensure that the data-word is

read before the next conversion is complete. If the user has not

read the conversion before the completion of the next

conversion, or if insufficient serial clocks are applied to the

AD7787 to read the word, the serial output register is reset

when the next conversion is complete, and the new conversion

is placed in the output serial register.

To exit the continuous read mode, the instruction 001110XX

must be written to the communications register while the RDY

pin is low. While in the continuous read mode, the ADC

monitors activity on the DIN line so that it can receive the

instruction to exit the continuous read mode. Additionally, a

reset occurs if 32 consecutive 1s are seen on DIN. Therefore,

DIN should be held low in continuous read mode until an

instruction is written to the device.

DIN

SCLK

DOUT/RDY

0x3C

DATA

Figure 15. Continuous Read

AD7787 Datasheet(PDF) 17 Page - Analog Devices