EMC1822 datasheet(34/103 Pages) MICROCHIP

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8.7

SMBus and I2C Compliance

The major differences between SMBus and I2C devices include the following:

•

Minimum frequency for SMBus communications is 10 kHz

•

The client protocol resets if the clock is held low for longer than 30 ms

•

Except when operating in the Standby mode, the client protocol resets if both the clock and the

data line are high for longer than 150 µs (Idle condition)

•

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

For complete compliance information, refer to “Application Note 14.0 - Microchip Dedicated Slave

Devices in I2C™ Systems” (DS00001853)

8.8

SMBus Protocols

The EMC1822/23/24/25/43 devices are SMBus 2.0 compatible and support send byte, read byte, block

read, receive byte as valid protocols, as shown below. They also support the I2C Block Read and Block

Write protocols. The device supports write byte, read byte and block read/block write.

All of the protocols below use the convention in the SMBus Protocol table.

Table 8-1. SMBus Protocol

Data Sent to Device

Data Sent to the Host

# of bits sent

8.8.1

SMBus Write Byte

The Write Byte is used to write one byte of data to a specific register, as shown in the following table.

Table 8-2. SMBus Write Byte Protocol

START

Slave Address

WR ACK Register Address

ACK Register Data

ACK STOP

1 → 0

YYYY_YYY

XXh

0 → 1

8.8.2

Block Write

The Block Write is used to write multiple data bytes to a group of contiguous registers, as shown below. It

is an extension of the Write Byte protocol.

Table 8-3. Block Write Protocol

START

Slave Address

WR ACK Register Address

ACK Repeat N Times

STOP

ACK

1 → 0

YYYY_YYY

XXh

0 → 1

Note: When using the Block Write protocol, the internal Address Pointer will be automatically

incremented after every data byte is received. It will wrap from FFh to 00h.

Note: The Block Write and Block Read protocols require that the Address Pointer be automatically

incremented. For a write command, the Address Pointer will be automatically incremented when the ACK

is sent to the host. There is no over or under bound limit checking and the Address Pointer will wrap

around from FFh to 00h if necessary.

Multi-Channel Low Voltage Temp Sens...

System Management Bus Protocol

Datasheet

DS20006048A-page 34

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