
Principles of Operation
62
September 2005
SCPS110
3.7.6 SMI Support in the PCIxx12 Controller
The PCIxx12 controller provides a mechanism for interrupting the system when power changes have been
made to the PC Card socket interfaces. The interrupt mechanism is designed to fit into a system maintenance
interrupt (SMI) scheme. SMI interrupts are generated by the controller, when enabled, after either a write cycle
to the socket control register (CB offset 10h, see Section 6.5) of the CardBus register set, or the ExCA power
control register (ExCA offset 02h/802h, see Section 5.3) causes a power cycle change sequence to be sent
on the power switch interface.
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 313
describes the SMI control bits function.
Table 313. SMI Control
BIT NAME
FUNCTION
SMIROUTE
This shared bit controls whether the SMI interrupts are sent as a CSC interrupt or as IRQ2.
SMISTAT
This socket-dependent bit is set when an SMI interrupt is pending. This status flag is cleared by writing back a 1b.
SMIENB
When set, SMI interrupt generation is enabled.
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/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 4.35).
3.8
Power-Management Overview
In addition to the low-power CMOS technology process used for the PCIxx12 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