AD5337ARM datasheet(18/24 Pages) AD

18 / 24 page

AD5337/AD5338/AD5339

Rev. A | Page 18 of 24

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 0. 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 may 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.

DATA BYTE

LEAST SIGNIFICANT DATA BYTE

R/W

LSB

ACK

AD533x

SCL

SDA

START

CONDITION

MASTER

ACK

AD533x

MSB

SCL

SDA

R/W

MSB

REPEATED

START

CONDITION

MASTER

ACK

AD533x

ADDRESS BYTE

SCL

SDA

MSB

LSB

ACK

MASTER

STOP

CONDITION

MASTER

POINTER BYTE

ADDRESS BYTE

ACK

MASTER

LSB

Figure 34. Read Sequence

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