PIIX3 datasheet(38/122 Pages) INTEL

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82371FB (PIIX) AND 82371SB (PIIX3)

Bit

Description

PIIX: Reserved.

PIIX3: EXTSMI# Mode Enable (ESMIME)

R/W. 1=Enable. 0=Disable (default). This bit is

used to enable a special SERR# handling protocol between the host-to-PCI bridge and the

PIIX3. When ESMIME is enabled, the operating mode of the EXTSMI# signal is determined

by the duration of the EXTSMI# signal. If the EXTSMI# signal is asserted for one PCLK, an

SERR# is reported in the NMISC Register (address 61h) and an NMI is generated, if enabled

in the NMI Registers (address 61h and 70h). If EXTSMI# is asserted for more than one

PCLK, the standard mode for handling EXTSMI# is used (i.e., same as when this bit is set to

0).

When disabled (standard mode) and a falling edge is detected on EXTSMI#, an SMI is

signaled, if EXTSMI# signaling is enabled.

Host-to-PCI

Bridge

SERR#

Gate not necessary

if system EXTSMI#

is not used

System EXTSMI#

(Assumes minimum

assertion of more

than one PCLK)

EXTSMI#

PIIX3

SMI_NMI.drw

Reserved.

PIIX: Reserved.

PIIX3: USB Enable (USBE)

R/W. 1=Enable. 0=Disable (default). When disabled, all USB

functionality is disabled. This bit must be set to 1 to access function 2 configuration space.

Note that dynamically disabling USB is not supported in PIIX3. This bit is used to

enable/disable the USB at boot time. In case software has to disable the USB during run time

it has to do the following: Software must turn off the master enable and I/O Decode Enable

for function 2 (via the PCICMD Register, function 2) prior to writing this bit to 0.

Reserved.

PIIX: PCI Header Type Bit Enable

R/W. This bit controls the Header Type Bit in the PIIX

(Multifunction device) and should be left in the default state.

PIIX3: Reserved.

PIIX: Internal ISA DMA or External DMA Mode Status (IEDMAS)

RO. 0=Normal DMA

Operation. This bit reports the strapping option selected on the TC signal (pulled high at reset

for a value of 0).

PIIX3: Reserved,

PIIX3 Scheda tecnica(PDF) 38 Page - Intel Corporation

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