emc2104 Standard Microsystems Corp., emc2104 Datasheet - Page 18

• Manufacturer Part Number: emc2104
• Description: Emc2104 Dual Rpm-based Pwm Fan Controller With Hardware Thermal Shutdown
• Manufacturer: Standard Microsystems Corp.

Chapter 4 Communications
Revision 1.74 (05-08-08)
4.1
4.2
SMDATA
START
0 -> 1
SMCLK
The EMC2104 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
however the EMC2104 will not stretch the clock signal.
The EMC2104 powers up as an SMBus client.
The EMC2104 contains a single SMBus interface. The SMBus address is determined by the
ADDR_SEL pin (see
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
The Write Byte is used to write one byte of data to the registers as shown below
ADDRESS
System Management Bus Interface Protocol
Write Byte
0101_111
P
SLAVE
T
BUF
S
T
T
S - Start Condition
HD:STA
LOW
WR
0
T
Section
HD:DAT
T
RISE
Figure 4.1 SMBus Timing Diagram
# of bits sent
DATA SENT
ACK
TO DEVICE
Table 4.2 Write Byte Protocol
0
Table 4.1 Protocol Format
4.7)The EMC2104 client interfaces are SMBus 2.0 compatible and
T
HIGH
DATASHEET
Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
REGISTER
ADDRESS
T
SU:DAT
T
XXh
FALL
18
DATA SENT TO
# of bits sent
Figure
THE HOST
Table
4.1. Stretching of the SMCLK signal is supported,
4.1.
ACK
0
S
T
T
SU:STA
HD:STA
REGISTER
DATA
XXh
P - Stop Condition
Table
ACK
0
T
SU:STO
SMSC EMC2104
4.2:
Datasheet
STOP
1 -> 0
P