Fan Control Device with High Frequency PWM and Temperature Monitors
Datasheet
Chapter 5 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.
5.1
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 EMC2300 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 EMC2300
address. This feature eliminates the possibility of a glitch on the SMBus interfering with address
selection.
Table 5.1 SMBus Slave Address Options
ADDRESS
ADDRESS
ENABLE#
SELECT
BOARD IMPLEMENTATION
SMBUS ADDRESS [7:1]
1
X
Address Enable# pulled to VCC through resistor
0101 110b
(default)
Note:
Resistor value will be dependent on PWM
circuit implemented.
0
0
0
1
Address Enable# pulled to ground through 10kΩ
0101 100b
0101 101b
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
In this way, there can be up to three EMC2300 devices on the SMBus at any time. Multiple EMC2300
devices can be used to monitor additional processors and temperature zones.
SMSC EMC2300
Revision 0.2 (06-14-06)
DATA1S5HEET
SMSC [ SMSC CORPORATION ]
