Protocols Overview

Intel® Pentium® Silver and Intel® Celeron® Processors

Datasheet, Volume 1 of 2

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ID 633935

Date 12/27/2022

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For more information on the I²C protocols and command formats, refer to the industry I2C specification. Below is a simplified description of I²C bus operation:

The master generates a START condition, signaling all devices on the bus to listen for data.
The master writes a 7-bit address, followed by a read/write bit to select the target device and to define whether it is a transmitter or a receiver.
The target device sends an acknowledge bit over the bus. The master must read this bit to determine whether the addressed target device is on the bus.
Depending on the value of the read/write bit, any number of 8-bit messages can be transmitted or received by the master. These messages are specific to the I²C device used. After 8 message bits are written to the bus, the transmitter will receive an acknowledge bit. This message and acknowledge transfer continues until the entire message is transmitted.
The message is terminated by the master with a STOP condition. This frees the bus for the next master to begin communications. When the bus is free, both data and clock lines are high.

Data Transfer on I2C Bus

Combined Formats

The PCH I2C controllers support mixed read and write combined format transactions in both 7-bit and 10-bit addressing modes.

The PCH controllers do not support mixed address and mixed address format (which means a 7-bit address transaction followed by a 10-bit address transaction or vice versa) combined format transaction.

To initiate combined format transfers, IC_CON.IC_RESTSART_EN should be set to 1. With this value set and operating as a master, when the controller completes an I2C transfer, it checks the transmit FIFO and executes the next transfer. If the direction of this transfer differs from the previous transfer, the combined format is used to issue the transfer. If the transmit FIFO is empty when the current I2C transfer completes, a STOP is issued and the next transfer is issued following a START condition.