AD7788ARMZ datasheet(16/20 Pages) AD

16 / 20 page

AD7788/AD7789

Rev. B | Page 16 of 20

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 is automatically 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 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 be read only

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

before the next conversion is complete.

If the data-word 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 continuous read mode, the instruction 001110XX must

be written to the communications register while the DOUT/

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

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

instruction to exit 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 to be written to the device.

DIN

SCLK

DOUT/RDY

0x3C

DATA

Figure 13. Continuous-Read Mode

AD7788ARMZ Datasheet(PDF) 16 Page - Analog Devices