EMC2305 Datasheet, PDF (15/55 Pages) SMSC Corporation – Multiple RPM-Based PWM Fan Controller for Five Fans

Multiple RPM-Based PWM Fan Controller for Five Fans
Datasheet
5. The Block Read and Block Write protocols are only compliant with I²C data formatting. They do
not support SMBus formatting for Block Read and Block Write protocols.
3.2
SMBus Protocols
The EMC2305 is SMBus 2.0 compatible and supports Send Byte, Read Byte, Receive Byte and Write
Byte as valid protocols as shown below. It will respond to the Alert Response Address protocol but is
not in full compliance.
All of the below protocols use the convention in Table 3.2. When reading the protocol blocks, the value
of YYYY_YYYb should be replaced with the respective SMBus addresses.
3.2.1
Table 3.2 Protocol Format
DATA SENT
TO DEVICE
# of bits sent
DATA SENT TO
THE HOST
# of bits sent
Write Byte
The Write Byte is used to write one byte of data to the registers as shown below Table 3.3.
SLAVE
START ADDRESS
WR
1 -> 0 YYYY_YYYb
0
Table 3.3 Write Byte Protocol
ACK
0
REGISTER
ADDRESS
XXh
ACK
0
REGISTER
DATA
XXh
ACK
0
STOP
0 -> 1
3.2.2
Read Byte
The Read Byte protocol is used to read one byte of data from the registers as shown in Table 3.4.
START
SLAVE
WR
ADDRESS
1 -> 0 YYYY_YYYb 0
ACK
0
Table 3.4 Read Byte Protocol
Register
Address
XXh
ACK START
Slave
Address
RD ACK
0
0 -> 1 YYYY_YYYb
1
0
Register
Data
XXh
NACK STOP
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 3.5.
START
1 -> 0
SLAVE
ADDRESS
YYYY_YYYb
Table 3.5 Send Byte Protocol
REGISTER
WR
ACK
ADDRESS
0
0
XXh
ACK
0
STOP
0 -> 1
SMSC EMC2305
15
DATASHEET
Revision 1.1 (10-12-09)