AD7798 datasheet(21/28 Pages) AD

21 / 28 page

Data Sheet

AD7798/AD7799

Rev. B | Page 21 of 28

Continuous Read

Rather than write to the communication register to access the

data each time a conversion is complete, the AD7798/AD7799

can be configured so that the conversions are placed on the

DOUT/RDY line automatically. By writing 01011100 to the

communication register, the user need only apply the

appropriate number of SCLK cycles to the ADC, and 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, 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. In addition, the user must ensure that the data-word is

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

read the conversion before the completion of the next conversion,

or if insufficient serial clocks are applied to the AD7798/AD7799

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 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 in case the instruction

to exit the continuous-read mode occurs. 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 18. Continuous Read

AD7798 Datasheet(PDF) 21 Page - Analog Devices