307013-003 Datasheet, PDF (220/848 Pages) Intel Corporation – Intel I/O Controller Hub 7

Functional Description
5.21.1
5.21.1.1
Host Controller
The SMBus host controller is used to send commands to other SMBus slave devices.
Software sets up the host controller with an address, command, and, for writes, data
and optional PEC; and then tells the controller to start. When the controller has finished
transmitting data on writes, or receiving data on reads, it generates an SMI# or
interrupt, if enabled.
The host controller supports 8 command protocols of the SMBus interface (see System
Management Bus (SMBus) Specification, Version 2.0): Quick Command, Send Byte,
Receive Byte, Write Byte/Word, Read Byte/Word, Process Call, Block Read/Write, Block
Write–Block Read Process Call, and Host Notify.
The SMBus host controller requires that the various data and command fields be setup
for the type of command to be sent. When software sets the START bit, the SMBus Host
controller performs the requested transaction, and interrupts the processor (or
generates an SMI#) when the transaction is completed. Once a START command has
been issued, the values of the “active registers” (Host Control, Host Command,
Transmit Slave Address, Data 0, Data 1) should not be changed or read until the
interrupt status bit (INTR) has been set (indicating the completion of the command).
Any register values needed for computation purposes should be saved prior to issuing
of a new command, as the SMBus host controller updates all registers while completing
the new command.
Using the SMB host controller to send commands to the ICH7’s SMB slave port is
supported. The ICH7 supports the System Management Bus (SMBus) Specification,
Version 2.0. Slave functionality, including the Host Notify protocol, is available on the
SMBus pins. The SMLink and SMBus signals should not be tied together externally.
Command Protocols
In all of the following commands, the Host Status Register (offset 00h) is used to
determine the progress of the command. While the command is in operation, the
HOST_BUSY bit is set. If the command completes successfully, the INTR bit will be set
in the Host Status Register. If the device does not respond with an acknowledge, and
the transaction times out, the DEV_ERR bit is set. If software sets the KILL bit in the
Host Control Register while the command is running, the transaction will stop and the
FAILED bit will be set.
Quick Command
When programmed for a Quick Command, the Transmit Slave Address Register is sent.
The PEC byte is not appended to the Quick Protocol. Software should force the PEC_EN
bit to 0 when performing the Quick Command. Software must force the I2C_EN bit to 0
when running this command. See section 5.5.1 of the System Management Bus
(SMBus) Specification, Version 2.0 for the format of the protocol.
Send Byte / Receive Byte
For the Send Byte command, the Transmit Slave Address and Device Command
Registers are sent
For the Receive Byte command, the Transmit Slave Address Register is sent. The data
received is stored in the DATA0 register. Software must force the I2C_EN bit to 0 when
running this command.
The Receive Byte is similar to a Send Byte, the only difference is the direction of data
transfer. See sections 5.5.2 and 5.5.3 of the System Management Bus (SMBus)
Specification, Version 2.0 for the format of the protocol.
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Intel ^® ICH7 Family Datasheet