FW82371EB Intel, FW82371EB Datasheet - Page 31

• Manufacturer Part Number: FW82371EB
• Manufacturer: Intel

Specifications of FW82371EB

• Lead Free Status / RoHS Status: Not Compliant

6.
7.
Specification Update
R
Continuous (Idle) Mode
In this mode, PIIX4 initiates the START frame, rather than the peripherals. Typically, this is done to
update IRQ status (acknowledges). PIIX4 drives SERIRQ low for 4–8 clocks. This is the default mode
after reset, and can be used to enter the Quiet mode.
Data Frame
Once the Start frame has been initiated, all of the serial interrupt peripherals must start counting frames
based on the rising edge of SERIRQ. Each of the IRQ/DATA frames has exactly 3 phases of 1 clock
each: a Sample phase, a Recovery Phase, and a Turn-around phase.
During the Sample phase, the device drives SERIRQ low if the state of the corresponding interrupt is
low. If the state of the corresponding interrupt is high the devices should not drive the SERIRQ signal. It
will remain high due to pull-up resistors. The PIIX4’s 8259 logic determines if the logic level on the
SERIRQ signal is active or inactive.
During the other two phases (Turn around and Recovery), no device should drive the SERIRQ signal.
The IRQ/DATA frames have a specific order and usage, as shown in Table 26.
If an SMI# is activated on frame 3, PIIX4 drives its EXTSMI# signal active. This then generates an
SMI# to the microprocessor, if enabled.
RI# Pulse Width Requirement
Section 11.4.2 of the PIIX4 datasheet specifies a 2 RTC pulse width requirement for GPI1,
IRQ[15:9,7:3,1], and USB resume events. This list should also include RI#.
This clarification applies to all steppings of the PIIX4 and will be incorporated into the next revision of
the PIIX4 datasheet.
“The GPI1, EXTSMI#, IRQ[15:9,7:3,1], and USB resume events must be active for a minimum of 64 s
(approximately 2 TC clock periods) for the resume to be recognized.”
Diode Requirement for Vref Sequencing Circuit
Figure 2, in section 2.3, of the PIIX4 datasheet provides an example Vref Sequencing Circuit. Included
in this circuit is a diode. The datasheet does not explicitly state that this diode should be a Schottky
diode.
This clarification applies to all steppings of the PIIX4 and will be incorporated into the next revision of
the PIIX4 datasheet.
Intel
®
82371EB (PIIX4E)
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