Environmental Monitoring and Control Device
Datasheet
Chapter 5 SMBus Interface
The host processor communicates with the Environmental Monitoring and Control device (EMC), 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 EMC6D100/EMC6D101 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
EMC6D100/EMC6D101 address. This feature eliminates the possibility of a glitch on the SMBus interfering
with address selection.
ADDRESS SELECT
BOARD IMPLEMENTATION
Pulled to ground through a 10kΩ resistor
Pulled to 3.3V through a 10kΩ resistor
SMBUS ADDRESS
0101100b
0101101b
0
1
In this way, there can be up to three EMC6D100/EMC6D101 devices on the SMBus at any time. Multiple
EMC6D100/EMC6D101 devices can be used to monitor additional processors and temperature zones.
Address Decided
Start
0
1
0
1
1
SDA
SCL
First five address bits
FIGURE 5.1 - ADDRESS SELECTION ON EMC6D100/EMC6D101
5.2
SMBus Slave Interface
The EMC6D100/EMC6D101 Device SMBus implementation is a subset of the SMBus interface to the host.
The Device is a slave-only SMBus device. The implementation in the Device is a subset of SMBus since it
only supports four protocols.
SMSC EMC6D100/EMC6D101
Page 16
Rev. 09-09-04
DATASHEET
SMSC [ SMSC CORPORATION ]
