BU8272GUW Datasheet, PDF (10/18 Pages) Rohm – GPIO Expander IC

BU8272GUW
Technical Note
1.6 Reading protocol
After Writing the slave address and Read/Write commend bits, the next byte is read. The reading register address is next of
previous accessed address. Therefore, the data is read with address increment. When the address in increased to the last,
the following read address will be reset to (00h). When the GPIO port [19:16] is read, 4 bits of “0” will be added from MSB,
and the value of 4 bits from GPIO port [19:16] is read from 2-wire interface.
S X X X X X X X 1 A D7 D6 D5 D4 D3 D2 D1 D0 A
Salve address
data
R/W=1(Read)
Register Address
increment
D7 D6 D5 D4 D3 D2 D1 D0 A P
data
Register address
increment
Transmit fronm master
Transmit from slave
A=acknowledge
A=not acknowledge
S=Start condition
P=Stop condition
Fig. 10 Readout protocol
1.7 Complex reading protocol
After the specifying the internal register address, a resending start condition occurs and the direction of data transfer is
changed then reading access is done. Therefore, the data is read followed by address increment. If the address is
increased to the last, it will be reset to (00h).
S X X X X X X X 0 A X X X X A3 A2 A1 A0 A Sr X X X X X X X 1 A
Slave address
Register address
Slave address
R/W=0(write)
R/W=1(read)
D7 D6 D5 D4 D3 D2 D1 D0 A
data
Transmit from master
Register address
increment
Transmit from slave
D7 D6 D5 D4 D3 D2 D1 D0 A P
data
A=acknowledge
A=not aclnowledge
S=Start condition
P=Stop condition
Sr=Start condition
Register address
increment
Fig. 11 Complex reading protocol
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10/17
2009.09 - Rev.A