RPM-Based PWM Fan Controller
Datasheet
3.2.2
Read Byte
The Read Byte protocol is used to read one byte of data from the registers as shown in
Table 3.3 Read Byte Protocol
START
SLAVE
ADDRESS
YYYY_YYYb
WR
ACK
Register
Address
XXh
ACK
START
Slave
Address
YYYY_YYYb
RD
ACK
Register
Data
XXh
NACK
STOP
1 -> 0
0
0
0
0 -> 1
1
0
1
0 -> 1
3.2.3
Send Byte
The Send Byte protocol is used to set the internal address register pointer to the correct address
location. No data is transferred during the Send Byte protocol as shown in
Table 3.4 Send Byte Protocol
SLAVE
ADDRESS
YYYY_YYYb
REGISTER
ADDRESS
XXh
START
1 -> 0
WR
0
ACK
0
ACK
0
STOP
0 -> 1
3.2.4
Receive Byte
The Receive Byte protocol is used to read data from a register when the internal register address
pointer is known to be at the right location (e.g. set via Send Byte). This is used for consecutive reads
of the same register as shown in
Table 3.5 Receive Byte Protocol
SLAVE
ADDRESS
YYYY_YYYb
START
1 -> 0
RD
1
ACK
0
REGISTER DATA
XXh
NACK
1
STOP
0 -> 1
3.2.5
Block Write Protocol
The Block Write is used to write multiple data bytes to a group of contiguous registers as shown in
It is an extension of the Write Byte Protocol.
Table 3.6 Block Write Protocol
SLAVE
ADDRESS
YYYY_YYYb
REGISTER
ADDRESS
XXh
REGISTER
DATA
XXh
START
1 ->0
REGISTER
DATA
XXh
WR
0
REGISTER
DATA
XXh
ACK
0
ACK
0
REGISTER
DATA
XXh
ACK
0
ACK
0
ACK
0
...
...
ACK
0
STOP
0 -> 1
Revision 1.1 (10-12-09)
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SMSC EMC2301
DATASHEET
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