The SMI control is programmed through three bits in the system control register (PCI offset 80h, see Section 4.29).
These bits are SMIROUTE (bit 26), SMISTATUS (bit 25), and SMIENB (bit 24). Table 3−12 describes the SMI control
bits function.
Table 3−12. SMI Control
BIT NAME
SMIROUTE
SMISTAT
FUNCTION
This shared bit controls whether the SMI interrupts are sent as a CSC interrupt or as IRQ2.
This socket-dependent bit is set when an SMI interrupt is pending. This status flag is cleared by writing back a 1.
When set, SMI interrupt generation is enabled. This bit is shared by functions 0 and 1.
SMIENB
If CSC SMI interrupts are selected, then the SMI interrupt is sent as the CSC on a per-socket basis. The CSC interrupt
can be either level or edge mode, depending upon the CSCMODE bit in the ExCA global control register (ExCA offset
1Eh/5Eh/81Eh, see Section 5.20).
If IRQ2 is selected by SMIROUTE, then the IRQSER signaling protocol supports SMI signaling in the IRQ2 IRQ/Data
slot. In a parallel ISA IRQ system, the support for an active low IRQ2 is provided only if IRQ2 is routed to either
MFUNC3 or MFUNC6 through the multifunction routing status register (PCI offset 8Ch, see Section 4.36).
3.8 Power Management Overview
In addition to the low-power CMOS technology process used for the PCI6x21/PCI6x11 controller, various features
are designed into the controller to allow implementation of popular power-saving techniques. These features and
techniques are as follows:
•
•
•
•
•
•
•
•
Clock run protocol
Cardbus PC Card power management
16-bit PC Card power management
Suspend mode
Ring indicate
PCI power management
Cardbus bridge power management
ACPI support
3−19
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