BU8272GUW Datasheet, PDF (8/18 Pages) Rohm – GPIO Expander IC

BU8272GUW
Technical Note
● Functional Description
1 2-Wire Bus Interface
1.1 Slave address
Please pull-up SDA and SCL to the same potential of voltage as DVDDI2C.
BU8272GUW is controlled by using an on-chip 2-Wire slave interface. Two kinds of the device address, “0001111” at
ADR=”1” or “0001000” at ADR=”0” can be used. The transfer bit rate supports Fast-mode up to max 400Kbps.
ADR=0
ADR=1
A7
A6
A5
A4
A3
A2
A1 W/R
0
0
0
1
0
0
0
0/1
0
0
0
1
1
1
1
2-Wire Slave address
Fig. 5 Slave address
1.2 Data transfer
One bit of data is transferred during SCL = “1”. During the bit transfer SCL = “1” cycle, the signal SDA should keep the
value. If SDA changes during SCL = “1”, a START condition or STOP condition occur and it is interpreted as a control
signal.
SDA
SCL
Data is valid
when SDA is
stable
SDA is
variable
Fig. 6 Data transfer
1.3 START-STOP conditions
When SDA and SCL are “1”, the data isn’t transferred on the 2-wire bus. If SCL remains “1” and SDA transfers from “1” to
“0”, it means a “Start condition” is occurred and access is started.
If SCL remains “1” and SDA transfers from “0” to “1”, it means a “Stop condition” is occurred and access is stopped.
SDA
SCL
S
START
condition
P
STOP
condition
Fig. 7 START-STOP conditions
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8/17
2009.09 - Rev.A