Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
Chapter 4 SMBus Interface
The host processor communicates with the Fan Monitoring device through a series of read/write
registers via the SMBus interface. SMBus is a serial communication protocol between a computer host
and its peripheral devices.
4.1
Slave Address
The default Slave Address is 0101110b. If this address is desired, the designer should not ground the
Address Enable# pin and should not apply a strapping resistor to the Address Select pin.
If multiple devices are implemented in a system or another SMBus device requires address 0101110b,
TACH4 and PWM3 must be disabled. In this case, addressing is implemented as follows:
The board designer will apply a 10KΩ pull-down resistor to ground on the Address Enable# pin. Upon
power up, the EMC6D102 device will be placed into Address Enable mode and assign itself an SMBus
address according to the Address Select input. The device will latch the address during the first valid
SMBus transaction in which the first five bits of the targeted address match those of the EMC6D102
address. This feature eliminates the possibility of a glitch on the SMBus interfering with address
selection.
Table 4.1 SMBus Slave Address Options
ADDRESS
ENABLE#
1
ADDRESS
SELECT
X
BOARD IMPLEMENTATION
Address Enable# pulled to VCC through resistor
Note:
0
0
Resistor value will be dependent on PWM
circuit implemented.
SMBUS ADDRESS [7:1]
0101 110b
(default)
Address Enable# pulled to ground through 10kΩ
resistor
Address Select Pulled to ground through a 10kΩ
resistor
Address Enable# pulled to ground through 10kΩ
resistor
Address Select pulled to VCC through a 10kΩ
resistor
0101 100b
0
1
0101 101b
In this way, there can be up to three EMC6D102 devices on the SMBus at any time. Multiple
EMC6D102 devices can be used to monitor additional processors and temperature zones.
SMSC EMC6D102
DATASHEET
13
Revision 0.4 (04-05-05)
SMSC [ SMSC CORPORATION ]
