EMC1187 datasheet(14/47 Pages) MICROCHIP

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Triple Channel 1°C Temperature Sensor with Hardware Thermal Shutdown and 1.8V SMBus Communications

Datasheet

Revision 1.0 (07-11-13)

SMSC EMC1187

DATASHEET

4.1.5

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 device detects an SMBus Stop bit

and it has been communicating with the SMBus protocol, it will reset its client interface and prepare

to receive further communications.

4.1.6

SMBus Timeout

The EMC1187 supports SMBus Timeout. If the clock line is held low for longer than tTIMEOUT, the

device will reset its SMBus protocol. This function can be enabled by setting the TIMEOUT bit (see

Section 6.13, "Consecutive ALERT Register 22h").

4.1.7

SMBus and I2C Compatibility

The EMC1187 is compatible with SMBus and I2C. The major differences between SMBus and I2C

devices are highlighted here. For more information, refer to the SMBus 2.0 and I2C specifications. For

information on using the EMC1187 in an I2C system, refer to SMSC AN 14.0 SMSC Dedicated Slave

Devices in I2C Systems.

1. EMC1187 supports I2C fast mode at 400kHz. This covers the SMBus max time of 100kHz.

2. Minimum frequency for SMBus communications is 10kHz.

3. The SMBus client protocol will reset if the clock is held at a logic ‘0’ for longer than 30ms. This

timeout functionality is disabled by default in the EMC1187 and can be enabled by writing to the

TIMEOUT bit. I2C does not have a timeout.

4. I2C devices do not support the Alert Response Address functionality (which is optional for SMBus).

Attempting to communicate with the EMC1187 SMBus interface with an invalid slave address or invalid

protocol will result in no response from the device and will not affect its register contents. Stretching

of the SMCLK signal is supported, provided other devices on the SMBus control the timing.

4.2

SMBus Protocols

The device supports Send Byte, Read Byte, Write Byte, Receive Byte, and the Alert Response Address

as valid protocols as shown below.

All of the below protocols use the convention in Table 4.1.

Table 4.1 Protocol Format

DATA SENT

TO DEVICE

DATA SENT TO

THE HOST

# of bits sent

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