REV. F

–14–

AD5305/AD5315/AD5325

READ OPERATION

When reading data back from the AD5305/AD5315/AD5325

DACs, the user begins with an address byte (R/

W = 0), after which

the DAC will acknowledge 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. Following

this, there is a repeated start condition by the master 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 9. A STOP

condition follows.

However, if the master sends an ACK and continues clocking

SCL (no STOP is sent), the DAC will retransmit the same two

bytes of data on SDA. This allows continuous readback 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 readback of data can commence immediately.

DATA BYTE

LEAST SIGNIFICANT DATA BYTE

00

0

1

1

A0

R/

W

XX

LSB

ACK

BY

AD53x5

SCL

SDA

START

COND

BY

MASTER

ACK

BY

AD53x5

MSB

SCL

SDA

00

0

1

1

0

A0

R/

W

MSB

LSB

ACK

BY

MASTER

REPEATED

START

COND

BY

MASTER

ACK

BY

AD53x5

ADDRESS BYTE

SCL

SDA

MSB

LSB

NO

ACK

BY

MASTER

STOP

COND

BY

MASTER

POINTER BYTE

ADDRESS BYTE

0

NOTE: DATA BYTES ARE THE SAME AS THOSE IN THE WRITE SEQUENCE EXCEPT THAT DON’T CARES ARE READ BACK AS 0s.

Figure 9. Readback Sequence