Datasheet

AD5337/AD5338/AD5339
Rev. C | Page 18 of 28
READ OPERATION
When reading data back from the AD5337/AD5338/AD5339
DACs, the user begins with an address byte (R/
W
= 0), after
which the DAC acknowledges that it is prepared to receive data
by pulling SDA low. This address byte is usually followed by the
pointer byte, which is also acknowledged by the DAC. Then, the
master initiates another start condition (repeated start) and the
address is resent with R/
W
= 1. This is acknowledged by the
DAC indicating that it is prepared to transmit data. Two bytes
of data are then read from the DAC as shown in
Figure 34. A
stop condition follows.
Note that in a read sequence, data bytes are the same as those in
the write sequence, except that don’t cares are read back as 0s.
However, if the master sends an ACK and continues clocking
SCL (no stop is sent), the DAC retransmits the same two bytes
of data on SDA. This allows continuous read back of data from
the selected DAC register. Alternatively, the user can send a
start followed by the address with R/
W
= 1. In this case, the
previously loaded pointer settings are used and read back of
data can begin immediately.
LEAST SIGNIFICANT DATA BYTE
000 11 X X
SCL
SDA
SCL
SDA
000 11
0
A0
SCL
SDA
0
03756-034
START
CONDITION
BY
MASTER
ADDRESS BYTE
A0 R/W
MSBACK
BY
AD533x
POINTER BYTE
LSB
ACK
BY
AD533x
ADDRESS BYTE
REPEATED
START
CONDITION
BY
MASTER
R/W
ACK
BY
AD533x
MSB
DATA BYTE
LSB
ACK
BY
MASTER
STOP
CONDITION
BY
MASTER
NO
ACK
BY
MASTER
LSBMSB
Figure 34. Read Sequence