AD7734 datasheet(25/32 Pages) AD

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AD7734

SERIAL

INTERFACE

START

CONTINUOUS

CONVERSION

RDY

CH0 CONVERSION

READ

DATA

CH1

CH1 CONVERSION

CH0 CONVERSION

READ

DATA

CH0

CH1 CONVERSION

READ

DATA

CH0

CH0 CONVERSION

READ

DATA

CH1

Figure 20. Continuous Conversion, CH0 and CH1, RDYFN = 1

SERIAL

INTERFACE

START

CONTINUOUS

CONVERSION

RDY

CH0 CONVERSION

CH1 CONVERSION

CH0 CONVERSION

CH1 CONVERSION

CH0 CONVERSION

Figure 21. Continuous Conversion, CH0 and CH1, No Data Read

DIN

48h

00h

DATA

00h

DATA

00h

STATUS

READ

CH0

DATA

READ

CH0

STATUS

48h

WRITE

COMM.

SCLK

DOUT

WRITE

COMM.

WRITE

MODE

RDY

38h

00h

DATA

00h

DATA

00h

STATUS

READ

CH1

DATA

READ

CH1

STATUS

CONVERSION

ON CH0

COMPLETE

CONVERSION

ON CH1

COMPLETE

Figure 22. Continuous Conversion, CH0 and CH1, Continuous Read

Continuous Read (Continuous Conversion) Mode

When the Cont RD bit in the mode register is set, the first write

of 48h to the communications register starts the continuous

read mode. As shown in Figure 22, 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

should 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 should be 0,

and reading the result should always start before the next

conversion is completed.

The AD7734 will stay in continuous read mode as long as the

DIN pin is low while the CS pin is low; therefore, write 0 to the

AD7734 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 80h to the AD7734 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 48h starts the

continuous read mode again. To completely stop the continuous

read mode, write to the mode register to clear the Cont RD bit.

Rev. 0 | Page 25 of 32

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