Datasheet

AD5272/AD5274 Data Sheet
Rev. D | Page 20 of 28
READ OPERATION
When reading data back from the AD5272/AD5274, the user
must first issue a readback command to the device, this begins
with a start command followed by an address byte (R/
W
= 0),
after which the AD5272/AD5274 acknowledges that it is
prepared to receive data by pulling SDA low.
Two bytes of data are then written to the AD5272/AD5274, the
most significant byte followed by the least significant byte; both
of these data bytes are acknowledged by the AD5272/AD5274.
A stop condition follows. These bytes contain the read instruc-
tion, which enables readback of the RDAC register, 50-TP
memory, or the control register. The user can then read back
the data beginning with a start command followed by an
address byte (R/
W
= 1), after which the device acknowledges
that it is prepared to transmit data by pulling SDA low. Two
bytes of data are then read from the device, as shown in Figure 45.
A stop condition follows. If the master does not acknowledge
the first byte, the second byte is not transmitted by the
AD5272/AD5274.
0
19
1
99
91
1
0 1 1 A1 A0 R/W 0 0 C3 C2 C1 C0 D9 D8
D7 D6 D5 D4 D3 D2 D1 D0
0
19
1
99
91
1
0 1 1 A1 A0 R/W 0 0 X X X X D9 D8
D7 D6 D5 D4 D3 D2 D1 D0
ACK. BY
AD5272/AD5274
ACK. BY
AD5272/AD5274
ACK. BY
AD5272/AD5274
ACK. BY
AD5272/AD5274
ACK. BY
MASTER
NO ACK. BY
MASTER
08076-007
SCL
SD
A
SCL (CONTINUED)
SDA (CONTINUED)
SCL (CONTINUED)
SDA (CONTINUED)
START BY
MASTER
SCL
SD
A
START BY
MASTER
STOP BY
MASTER
STOP BY
MASTER
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
MOST SIGNIFICANT DATA BYTE
FRAME 2
MOST SIGNIFICANT DATA BYTE
FRAME 3
LEAST SIGNIFICANT DATA BYTE
FRAME 3
LEAST SIGNIFICANT DATA BYTE
Figure 45. Read Command