Datasheet

AD7790 Data Sheet
Rev. A | 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 AD7790 can be
placed in continuous read mode. By writing 001111XX to the
communications register, the user only needs to apply the
appropriate number of SCLK cycles to the ADC and the 16-bit
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 AD7790 to read
the word, the serial output register is reset when the next con-
version 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.
03538-0-011
DIN
SCLK
DOUT/RDY
CS
0x3C
DATA DATA DATA
Figure 10. Continuous Read