Datasheet
AD7739 Data Sheet
Rev. A | Page 24 of 32
CONTINUOUS READ (CONTINUOUS CONVERSION)
MODE
When the Cont RD bit in the mode register is set, the first write
of 0x48 to the communications register starts the continuous
read mode. As shown in Figure 21, subsequent accesses to the
part sequentially read the channel status and data registers of
the last completed conversion without any further configuration
of the communications register being required.
Note that the continuous conversion bit in the mode register
must be set when entering the continuous read mode.
Note that the continuous read mode is a dump mode reading of
the channel status and data registers regardless of the dump bit
value. Use the channel bits in the channel status register to
check/recognize which channel data is actually being
shifted out.
Note that the last completed conversion result is being read.
Therefore, the RDYFN bit in the I/O port register must be 0,
and reading the result must always start before the next
conversion is completed.
The AD7739 stays in continuous read mode as long as the DIN
pin is low while the
CS
pin is low; therefore, write 0 to the AD7739
while reading in continuous read mode. To exit continuous read
mode, take the DIN pin high for at least 100 ns after a read is
complete. (Write 0x80 to the AD7739 to exit continuous reading.)
Taking the DIN pin high does not change the Cont RD bit in
the mode register. Therefore, the next write of 0x48 starts the
continuous read mode again. To completely stop the continuous
read mode, write to the mode register to clear the Cont RD bit.
Figure 21. Continuous Conversion, CH0 and CH1, Continuous Read
DIN
0x48
(0x00)
DATA
(0x00)
DATA
(0x00)
STATUS
READ
CH0
DATA
READ
CH0
STATUS
0x48
WRITE
COMM.
REGISTER
SCLK
CS
DOUT
WRITE
COMM.
REGISTER
WRITE
MODE
REGISTER
RDY
0x38
(0x00)
DATA
(0x00)
DATA
(0x00)
STATUS
READ
CH1
DATA
READ
CH1
STATUS
CONVERSION
ON CH0
COMPLETE
CONVERSION
ON CH1
COMPLETE
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