AN2511 datasheet(10/43 Pages) STMICROELECTRONICS

10 / 43 page

Implementation of PMBus using ST7 I2C

AN2511

10/43

Doc ID 13286 Rev 2

Figure 5.

Flowchart: write operation

During the PMBus communication, if there are any errors in communication (acknowledge

failure, arbitration loss, bus error or SMBus timeout), the I2C peripheral is disabled. It is re-

initialized again inside the PMBus write/ read functions.

In case the SMBus Alert pin is pulled low by the slave to inform the master that it wants to

communicate, the slave address is programmed with the alert response address (0x18).

This is acknowledged by the slave that alerted the master. After the communication between

the master and slave is complete, the slave address is programmed with the user-defined

slave address. The default value of this user-defined address is 0x30.

In case of group operation, the write operation flowchart is followed without the stop

condition.

START

Check if SMBus_Mode for

Send Byte command

Check if SMBus_Mode for Write

Word command

Check if SMBus_Mode for

Write Block command

Yes

SMBus Send byte protocol

SMBus Write word protocol

SMBus Write block protocol

STOP

171

181

Slave Address

Data Byte

171

1818181

Slave Address

Command Code

Data Byte Low

Data Byte HIgh

...

Data Byte 2

...

Data Byte N

171

18181

181

Slave Address

Command Code

Byte Count = N

Data Byte 1

...

Yes

SMBus Write byte protocol

171

18181

Slave Address

Command Code

Data Byte

Check if SMBus_Mode for Write

Byte command

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