Datasheet

AD7195
Rev. 0 | Page 31 of 44
Continuous Read
Rather than write to the communications register each time
a conversion is complete to access the data, the AD7195 can
be configured so that the conversions are placed on the
DOUT/
RDY
line automatically. By writing 01011100 to
the communications register, the user need only apply the
appropriate number of SCLK cycles to the ADC, and the
conversion 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 then 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 user has not read
the conversion before the completion of the next conversion,
or if insufficient serial clocks are applied to the AD7195 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, Instruction 01011000 must
be written to the communications register while the
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 the continuous read mode. Additionally, a reset occurs
if 40 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.
When several channels are enabled, the ADC continuously
steps through the enabled channels and performs one con-
version on each channel each time that it is selected. DOUT/
RDY
pulses low when a conversion is available. When the user
applies sufficient SCLK pulses, the data is automatically placed
on the DOUT/
RDY
pin. If the DAT_STA bit in the mode
register is set to 1, the contents of the status register are output
along with the conversion. The status register indicates the
channel to which the conversion corresponds.
DIN
SCLK
DOUT/RDY
CS
0x5C
DATA DATA DATA
0
8771-031
Figure 23. Continuous Read