2-Wire-Interfaced 8-Bit I/O Port Expander

with Reset

______________________________________________________________________________________

13

13

24

5

8

67

SA

A

A

0

A5

A4

A3A2

A1A0

DATA 1

SLAVE ADDRESS

DATA TO PORT

START CONDITION

ACKNOWLEDGE

FROM SLAVE

ACKNOWLEDGE

FROM SLAVE

ACKNOWLEDGE

FROM SLAVE

DATA 1 VALID

9

1

0

0

00

COMMAND BYTE

P

DATA OUT

FROM PORT

WRITE TO

PORT

SDA

SCL

0

00

0

R/W

Figure 9. Write to Output Port Register Through Write-Byte Protocol

S1

A

A

0

A2

A1

A0

DATA 4

SLAVE ADDRESS

DATA FROM PORT

START CONDITION

NOTE 1: THIS FIGURE ASSUMES THE COMMAND HAS PREVIOUSLY BEEN PROGRAMMED WITH 0x00.

NOTE 2: TRANSFER OF DATA CAN BE STOPPED AT ANY MOMENT BY A STOP CONDITION. WHEN THIS OCCURS,

DATA PRESENT AT THE LAST ACKNOWLEDGED PHASE IS VALID (OUTPUT MODE). INPUT DATA IS LOST.

R/W

ACKNOWLEDGE

FROM SLAVE

ACKNOWLEDGE

FROM MASTER

STOP

CONDITION

DATA 1

DATA FROM PORT

P

DATA 4

DATA 3

DATA 2

DATA INTO

PORT

WRITE FROM

PORT

SDA

NA

NO ACKNOWLEDGE

FROM MASTER

A5

A4

A3

1

Figure 10. Read Input Port Register Through Receive-Byte Protocol