BU8272GUW Datasheet, PDF (13/18 Pages) Rohm – GPIO Expander IC

BU8272GUW
Technical Note
2.1 Write to GPIO Port
After setting the internal register address, the data from master is written from MSB.
After Acknowledge is returned, the value of each GPIO port will be changed.
・IOSEL=1
In the condition that IOSEL register is “1”, after sending Acknowledge, a value “0” is output from the GPIO port which the
corresponding bit is transferred as ‘0’, and a input-mode(Hi-Z) is output from GPIO port which the corresponding bit is
transferred as ‘1’.
SCL
1 2 3 45 6 78 9
SDA S X X X X X X X 0 Ack MSB
Reg Address
Start Condition
GPIO
[7:0]
Write
Acknowledge From Slave
GPIO
[15:8]
LSB Ack MSB
Data1 (GPIO[7:0])
LSB Ack MSB
Data2 (GPIO[15:8])
LSB Ack P
Acknowledge From Slave
Acknowledge From Slave
Stop Condition
Data1 Valid
tDV
tDV
Data2
Valid
Fig. 14 Write to GPIO port （Pull-up-mode）
・IOSEL=0
In the condition that IOSEL register is “0”, data input or output is defined by the value of RWSEL register. Therefore, after
“0” is written to each bit of RWSEL register, the data is output from GPIO port. If “0” is written to RWSEL register at first, the
data will be output immediately from the GPIO port after the acknowledge signaling.
SCL
1 2 3 45 6 78 9
SDA S X X X X X X X 0 Ack MSB
Reg Address
Start Condition
GPIO
[7:0]
Write
Acknowledge From Slave
GPIO
[15:8]
LSB Ack MSB
Data1 (GPIO[7:0])
LSB Ack MSB RWSEL = Write Mode LSB Ack P
Acknowledge From Slave
Acknowledge From Slave
Stop Condition
tDV
tDV
Data1
Valid
Data2
Valid
Fig. 15 Write to GPIO port （RWSEL-mode）
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© 2009 ROHM Co., Ltd. All rights reserved.
13/17
2009.09 - Rev.A