EMC2113 datasheet(18/88 Pages) MICROCHIP

18 / 88 page

RPM-Based Fan Controller with Multiple Temperature Zones & Hardware Thermal Shutdown

Datasheet

DS20005251A-page 18

 2013 Microchip Technology Inc.

5.1.3

SMBus Data Bytes

All SMBus Data bytes are sent most significant bit first and composed of 8-bits of information.

5.1.4

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

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.

5.1.6

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").

5.1.7

SMBus and I2C 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.

22k Ohm ±5%

1001_101(r/w)

33k Ohm ±5%

1001_000(r/w)

Table 5.1 ADDR_SEL Pin Decode (continued)

PULL-UP RESISTOR VALUE

FAN CONTROL ADDRESS

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