82801FB Datasheet, PDF (221/786 Pages) Intel Corporation – Intel I/O Controller Hub 6 (ICH6) Family

Functional Description
5.21.5 SMBALERT#
SMBALERT# is multiplexed with GPI[11]. When enable and the signal is asserted, The ICH6 can
generate an interrupt, an SMI#, or a wake event from S1–S5.
Note: Any event on SMBALERT# (regardless whether it is programmed as a GPI or not), causes the
event message to be sent in heartbeat mode.
5.21.6
SMBus CRC Generation and Checking
If the AAC bit is set in the Auxiliary Control register, the ICH6 automatically calculates and drives
CRC at the end of the transmitted packet for write cycles, and will check the CRC for read cycles.
It will not transmit the contents of the PEC register for CRC. The PEC bit must not be set in the
Host Control register if this bit is set, or unspecified behavior will result.
If the read cycle results in a CRC error, the DEV_ERR bit and the CRCE bit in the Auxiliary Status
register at offset 0Ch will be set.
5.21.7 SMBus Slave Interface
The ICH6’s SMBus slave interface is accessed via the SMBus. The SMBus slave logic will not
generate or handle receiving the PEC byte and will only act as a Legacy Alerting Protocol device.
The slave interface allows the ICH6 to decode cycles, and allows an external microcontroller to
perform specific actions. Key features and capabilities include:
• Supports decode of three types of messages: Byte Write, Byte Read, and Host Notify.
• Receive Slave Address register: This is the address that the ICH6 decodes. A default value is
provided so that the slave interface can be used without the processor having to program this
register.
• Receive Slave Data register in the SMBus I/O space that includes the data written by the
external microcontroller.
• Registers that the external microcontroller can read to get the state of the ICH6.
• Status bits to indicate that the SMBus slave logic caused an interrupt or SMI# due to the
reception of a message that matched the slave address.
— Bit 0 of the Slave Status Register for the Host Notify command
— Bit 16 of the SMI Status Register (Section 10.8.3.13) for all others
If a master leaves the clock and data bits of the SMBus interface at 1 for 50 µs or more in the
middle of a cycle, the ICH6 slave logic's behavior is undefined. This is interpreted as an
unexpected idle and should be avoided when performing management activities to the slave logic.
Note:
When an external microcontroller accesses the SMBus slave interface over the SMBus a
translation in the address is needed to accommodate the least significant bit used for read/write
control. For example, if the ICH6 slave address (RCV_SLVA) is left at 44h (default), the external
micro controller would use an address of 88h/89h (write/read).
Intel^® I/O Controller Hub 6 (ICH6) Family Datasheet
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