AD7785 datasheet(24/32 Pages) AD

24 / 32 page

AD7785

Rev. 0 | Page 24 of 32

Continuous Read

Rather than write to the communications register to access

the data each time a conversion is complete, the AD7785

can be configured so that the conversions are placed on the

DOUT/RDY line automatically. By writing 01011100 to the

communications register, the user needs only to apply the 24

SCLK cycles to the ADC, and the 20-bit result followed by four

1s 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 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. In addition, 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

AD7785 to read the word, the serial output register is reset

when the next conversion is completed, 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 communications register while the

DOUT/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

0x5C

DATA

Figure 19. Continuous Read

AD7785 Datasheet(PDF) 24 Page - Analog Devices