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AD7788BRM

Low Power, 16-/24-Bit Sigma-Delta ADC

Analog Devices 

AD7788/AD7789

Continuous Read Mode

Rather than write to the communications register each time a

conversion is complete to access the data, the AD7788/AD7789

can be placed in continuous read mode. By writing 001111XX

to the communications register, the user needs only to apply the

appropriate number of SCLK cycles to the ADC and the data

word will automatically be placed on the DOUT/RDY line

when a conversion is complete.

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

sion, sufficient SCLK cycles must be applied to the ADC and the

data conversion will be placed on the DOUT/RDY line. When

the conversion is read, DOUT/RDY will return high until the

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

only 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 AD7788/AD7789

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 will occur if 32 consecutive 1s are seen on DIN. Therefore,

DIN should be held low in continuous read mode until an

instruction is to be written to the device.

CS

DIN

DOUT/RDY

SCLK

CS

DIN

DOUT/RDY

SCLK

0x38

DATA

Figure 12. Continuous Conversion

0x38

DATA

03539-0-012

0x3C

DATA

DATA

Figure 13. Continuous Read

DATA

03539-0-011

Rev. 0 | Page 16 of 20

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