82801BA Datasheet, PDF (35/498 Pages) Intel Corporation – Intel 82801BA I/O Controller Hub 2 (ICH2) and Intel 82801BAM I/O Controller Hub 2 Mobile

Introduction
System Management Bus (SMBus)
The ICH2 contains an SMBus Host interface that allows the processor to communicate with
SMBus slaves. This interface is compatible with most I²C devices. Special I²C commands are
implemented (e.g., the I²C Read that allows the ICH2 to perform block reads of I²C devices).
The ICH2’s SMBus host controller provides a mechanism for the processor to initiate
communications with SMBus peripherals (slaves). The host controller supports seven SMBus
interface command protocols for communicating with SMBus slave devices (see System
Management Bus Specifications, Rev 1.0): Quick Command, Send Byte, Receive Byte, Write
Byte/Word, Read Byte/Word, Process Call, and Block Read/Write.
Manageability
The ICH2 integrates several functions designed to manage the system and lower the total cost of
ownership (TC0) of the system. These system management functions are designed to report errors,
diagnose the system, and recover from system lockups without the aid of an external
microcontroller.
• TCO Timer. The ICH2’s integrated programmable TC0 Timer is used to detect system locks.
The first expiration of the timer generates an SMI# that the system can use to recover from a
software lock. The second expiration of the timer causes a system reset to recover from a
hardware lock.
• Processor Present Indicator. The ICH2 looks for the processor to fetch the first instruction
after reset. If the processor does not fetch the first instruction, the ICH2 will reboot the system
at the safe-mode frequency multiplier.
• ECC Error Reporting. When detecting an ECC error, the host controller has the ability to
send one of several messages to the ICH2. The host controller can instruct the ICH2 to
generate either an SMI#, NMI, SERR#, or TCO interrupt.
• Function Disable. The ICH2 provides the ability to disable the following functions: AC’97
Modem, AC’97 Audio, IDE, USB, or SMBus. Once disabled, these functions no longer
decode I/O, memory, or PCI configuration space. Also, no interrupts or power management
events are generated from the disable functions.
• Intruder Detect. The ICH2 provides an input signal (INTRUDER#) that can be attached to a
switch that is activated by the system case being opened. The ICH2 can be programmed to
generate an SMI# or TCO interrupt due to an active INTRUDER# signal.
• SMBus. The ICH2 integrates an SMBus controller that provides an interface to manage
peripherals (e.g., serial presence detection (SPD) or RIMMs and thermal sensors).
• Alert-On-LAN*. The ICH2 supports Alert-On-LAN* and Alert-On-LAN* 2. In response to a
TCO event (intruder detect, thermal event, processor not booting) the ICH2 sends a message
over the SMBus. A LAN controller can decode this SMBus message and send a message over
the network to alert the network manager.
82801BA ICH2 and 82801BAM ICH2-M Datasheet
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