RPM-Based Fan Controller with Multiple Temperature Zones & Hardware Thermal Shutdown
Datasheet
Table 5.1 ADDR_SEL Pin Decode (continued)
PULL-UP RESISTOR VALUE
FAN CONTROL ADDRESS
22k Ohm ±5%
33k Ohm ±5%
1001_101(r/w)
1001_000(r/w)
5.1.3
5.1.4
SMBus Data Bytes
All SMBus Data bytes are sent most significant bit first and composed of 8-bits of information.
SMBus ACK and NACK Bits
The SMBus slave will acknowledge all data bytes that it receives. This is done by the slave device
pulling the SMBus Data line low after the 8th bit of each byte that is transmitted.
The Host will NACK (not acknowledge) the last data byte to be received from the slave by holding the
SMBus data line high after the 8th data bit has been sent.
5.1.5
5.1.6
SMBus Stop Bit
The SMBus Stop bit is defined as a transition of the SMBus Data line from a logic ‘0’ state to a logic
‘1’ state while the SMBus clock line is in a logic ‘1’ state. When the EMC2113 detects an SMBus Stop
bit, and it has been communicating with the SMBus protocol, it will reset its slave interface and prepare
to receive further communications.
SMBus Time-out
The EMC2113 includes an SMBus time-out feature. Following a 30ms period of inactivity on the
SMBus, the device will time-out and reset the SMBus interface.
The SMBus timeout defaults to enabled and can be disabled by setting the DIS_TO bit (see Section
7.12, "Configuration 2 Register").
2
5.1.7
SMBus and I C Compliance
The major difference between SMBus and I2C devices is highlighted here. For complete compliance
information refer to the SMBus 2.0 specification.
1. Minimum frequency for SMBus communications is 10kHz.
2. The slave protocol will reset if the clock is held low longer than 30ms.
3. The slave protocol will reset if both the clock and the data line are high for longer than 150us (idle
condition).
4. I2C devices do not support the Alert Response Address functionality (which is optional for SMBus).
5.2
SMBus Protocols
The EMC2113 slave interface is SMBus 2.0 compatible and support Send Byte, Read Byte, Receive
Byte, Write Byte, Block Read Byte, Block Write 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 5.2, "Protocol Format". For the Slave Address
fields, the value of YYYY_YYY represents the programmed SMBus address.
Revision 1.2 (10-08-09)
SMSC EMC2113
DATA1S8HEET
SMSC [ SMSC CORPORATION ]
