RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
Chapter 4 Communications
4.1
System Management Bus Interface Protocol
The EMC2103 communicates with a host controller, such as an SMSC SIO, through the SMBus. The
SMBus is a two-wire serial communication protocol between a computer host and its peripheral
devices. A detailed timing diagram is shown in
Stretching of the SMCLK signal is supported,
however the EMC2103 will not stretch the clock signal.
T
LOW
T
HIGH
T
HD:STA
T
SU:STO
SMCLK
T
HD:STA
T
RISE
T
FALL
T
HD:DAT
T
SU:DAT
T
SU:STA
SMDATA
T
BUF
P
S
S - Start Condition
S
P - Stop Condition P
Figure 4.1 SMBus Timing Diagram
The EMC2103 contains a single SMBus interface. The EMC2103 client interfaces are SMBus 2.0
compatible and support Send Byte, Read Byte, Receive Byte and the Alert Response Address as valid
protocols. These protocols are used as shown below.
All of the below protocols use the convention in
Table 4.1 Protocol Format
DATA SENT
TO DEVICE
# of bits sent
DATA SENT TO
THE HOST
# of bits sent
4.2
Write Byte
The Write Byte is used to write one byte of data to the registers as shown below
Table 4.2 Write Byte Protocol
SLAVE
ADDRESS
0101_110
REGISTER
ADDRESS
0 -> 1
REGISTER
DATA
XXh
START
0 -> 1
WR
0
ACK
0
ACK
0
ACK
0
STOP
1 -> 0
SMSC EMC2103
17
Revision 0.85 (01-29-08)
DATASHEET
SMSC [ SMSC CORPORATION ]
