AN2511 datasheet(9/43 Pages) STMICROELECTRONICS

9 / 43 page

AN2511

Implementation of PMBus using ST7 I2C

Doc ID 13286 Rev 2

9/43

Figure 3.

Flowchart: data length calculation

Inside both PMBus_CommandRead and PMBus_CommandWrite functions,

PMBus_DataLengthCalc

is called which calculates the data length based on the

command code received.

2.1.3

Read and write operation

PMBus master performs read/ write operations with the slave device. Depending on the

command code, either PMBus_CommandRead or PMBus_CommandWrite is called. Inside

this function, the SMBus transaction type is selected as shown in the following sequence.

Figure 4.

Flowchart: read operation

START

Check if command code equal

to Block protocol

Check if command code equal

to Byte protocol

Check if command code equal

to word protocol

Yes

Byte Count=6,

Update

SMBus_Mode

for Block Command

Byte Count=1,

Update

SMBus_Mode

for Byte Command

Byte Count=2,

Update

SMBus_Mode

for Word Command

STOP

START

Check if SMBus_Mode for

Byte command

Check if SMBus_Mode for Word

command

Check if SMBus_Mode for

Send Block command

Yes

SMBus Read byte protocol

SMBus Read word protocol

SMBus Read block protocol

STOP

171

181

171

Slave Address

Command Code

Slave Address

Data Byte

171

181

171

181

Slave Address

Command Code

Slave Address

Data Byte Low

...

8181

...

Data Byte 1

Data Byte 2

...

Data Byte N

171

181

171

181

Slave Address

Command Code

Slave Address

Count Byte = 1

...

Data Byte High

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