AD7997 datasheet(26/32 Pages) AD

26 / 32 page

AD7997/AD7998

Rev. 0 | Page 26 of 32

READING DATA FROM THE AD7997/AD7998

Reading data from the AD7997/AD7998 is a 1- or 2-byte

operation. Reading back the contents of the alert status register

or the cycle timer register is a single-byte read operation, as

shown in Figure 29. This assumes the particular register address

has previously been set up by a single-byte write operation to

the address pointer register, as shown in Figure 26. Once the

performed from that particular register without having to write

to the address pointer register again.

If a read from a different register is required, the relevant

and again any number of reads from this register may then be

performed.

Reading data from the configuration register, conversion result

registers is a 2-byte operation, as shown in Figure 30. The same

rules apply for a 2-byte read as a single-byte read.

When reading data back from a register, for example the

conversion result register, if more than two read bytes are

supplied, the same or new data is read from the AD7997/

AD7998 without the need to readdress the device. This allows

the master to continuously read from a data register without

having to readdress the AD7997/AD7998.

SDA

R/W

SCL

START BY

MASTER

ACK. BY

AD7997/AD7998

NO ACK. BY

MASTER

STOP BY

MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

SINGLE DATA BYTE FROM AD7997/AD7998

Figure 29. Reading a Single Byte of Data from a Selected Register

SDA

ALERT

FLAG

CHID2

D10

SCL

D11

D1/0

D0/0

SCL (CONTINUED)

SDA (CONTINUED)

CHID1 CHID0

R/W

START BY

MASTER

ACK. BY

AD7997/AD7998

NO ACK. BY

MASTER

ACK. BY

MASTER

STOP BY

MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

MOST SIGNIFICANT DATA BYTE FROM

AD7997/AD7998

FRAME 2

MOST SIGNIFICANT DATA BYTE FROM

AD7997/AD7998

Figure 30. Reading Two Bytes of Data from the Conversion Result Register

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