EVAL-AD7797EB datasheet(19/24 Pages) AD

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AD7796/AD7797

Rev. A | Page 19 of 24

Continuous Read Mode

Rather than write to the communication register each time a

conversion is complete to access the data, the AD7796/AD7797

can be configured to automatically place the conversions on the

DOUT/RDY line. By writing 01011100 to the communication

SCLK cycles to the ADC. The 16-/24-bit word is automatically

placed on the DOUT/RDY line when a conversion is complete.

The ADC should be configured for continuous conversion mode.

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

sufficient SCLK cycles must be applied to the ADC. The data

conversion is placed on the DOUT/RDY line. When the conver-

sion is read, DOUT/RDY returns high until the next conversion

is available. In this mode, the data can be read only once.

The user must also 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 AD7796/AD7797 to

read the word, the serial output register is reset when the next

conversion is complete. The new conversion is placed in the

output serial register.

To exit continuous read mode, the instruction 01011000 must

be written to the communication register while the DOUT/RDY

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

activity on the DIN line to 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

0x5C

DATA

Figure 16. Continuous Read

EVAL-AD7797EB Datasheet(PDF) 19 Page - Analog Devices