CS5345

26

Since the read operation can not set the MAP, an aborted write operation is used as a preamble. As shown in

Figure 12, the write operation is aborted after the acknowledge for the MAP byte by sending a stop condition. The

following pseudocode illustrates an aborted write operation followed by a read operation.

Send start condition.

Send 10011xx0 (chip address & write operation).

Receive acknowledge bit.

Send MAP byte, auto increment off.

Receive acknowledge bit.

Send stop condition, aborting write.

Send start condition.

Send 10011xx1(chip address & read operation).

Receive acknowledge bit.

Receive byte, contents of selected register.

Send acknowledge bit.

Send stop condition.

Setting the auto increment bit in the MAP allows successive reads or writes of consecutive registers. Each

byte is separated by an acknowledge bit.

SCL

CHIP ADDRESS (WRITE)

MAP BYTE

DATA

DATA +1

START

ACK

STOP

ACK

ACK

ACK

1

0

0

1

1 AD1 AD0 0

SDA

1

0

0

1

1 AD1 AD0 1

CHIP ADDRESS (READ)

START

INCR

6

5

4

3

2

1

0

7

0

7

0

7

0

NO

16

8

9

12 13 14 15

4

5

6

7

0

1

20 21 22 23 24

26 27 28

2

3

10 11

17 18

19

25

ACK

DATA + n

STOP

Figure 12. Control Port Timing, I²C Read