AN2511 datasheet(8/43 Pages) STMICROELECTRONICS

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Implementation of PMBus using ST7 I2C

AN2511

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Doc ID 13286 Rev 2

Implementation of PMBus using ST7 I2C

2.1

Firmware architecture

This section explains sequence of operation for different software modules.

2.1.1

I2C initialization

To use ST7 I2C for PMBus communication, the peripheral is initialized for 100 kHz

communication speed. The I2C is configured with an address of 0x30, as it can act as a

slave due to its multi-master capability. The following flowchart shows the sequence.

Figure 2.

Flowchart: I2C initialization

The above flowchart is implemented in the function PMBus_Init.

2.1.2

Slave address and command code

The PMBus master addresses the slave with a 7-bit address. Once the slave device

acknowledges the address, the command code is sent corresponding to the PMBus

command and SMBus protocol (refer to Section 3.1).

Then, the microcontroller decodes the command code as shown in the following sequence.

Simultaneously, the SMBus_Mode variable is updated.

START

Initialize I2C CR, CCR,

OAR1 and OAR2 registers

Configure slave addresses

in OAR1 and OAR2

Enable I2C peripheral and

acknowledge in I2CCR register

Set communication speed as

100kHz in I2CCCR register

STOP

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