BU8272GUW ROHM Co. Ltd., BU8272GUW Datasheet - Page 9

• Manufacturer Part Number: BU8272GUW
• Description: Gpio Expander Ic
• Manufacturer: ROHM Co. Ltd.

© 2009 ROHM Co., Ltd. All rights reserved.
BU8272GUW
www.rohm.com
1.4 Acknowledge
After start condition is occurred, 8 bits data will be transferred. Then the “Master” opens SDA and “Slave” de-asserts SDA to
“0” as an “Acknowledge” returned.
1.5 Writing protocol
A writing protocol is shown in Fig.8-5 below. GPIO register address in BU8272GUW is transferred after one byte of slave
address with a write commend. The 3
byte transfer, the register address will be automatically increased. However, when the register address increased to the final
address (09h), it will be reset to (00h) after the byte transfer.
GPIO register address (00h) is assigned to GPIO register[7:0], the register address (01h) is assigned to GPIO register[15:8],
and the register address (02h) is assigned to GPIO register[19:16]. Only the 4 bits LSB data are valid in the register with
GPIO register address (02h).
S
X
X X
Slave address
X
from “Master”
from “Slave”
SDA output
SDA output
X X
Transmit from slave
SCL
Transmit from master
R/W=0(write)
X
0
START condition
A
X X X X A3 A2 A1 A0
rd
S
byte data is written to internal register which defined by the 2
Register address
Fig. 8 Acknowledge
Fig. 9 Writing protocol
1
9/17
A
D7 D6 D5 D4 D3 D2 D1 D0
A=acknowledge
A=not acknowledge
S=Start condition
P=Stop condition
2
Not acknowledge
For Acknowledgs
data
Acknowledg
Clock pulse
Register address
8
increment
e
A
9
D7 D6 D5 D4 D3 D2 D1 D0
nd
byte. After the each
Technical Note
2009.09 - Rev.A
data
Register address
increment
A P