
Advanced Notebook I/O for ISA or LPC Designs
Datasheet
SMSC SIO10N268
Page 151
Rev. 0.5 (03-24-05)
DATASHEET
Note 8.51
GP41-GP47 and GP51-GP57 should not be connected to any VTR powered external circuitry. These
pins are not used for wakeup.
8.17
System Management Interrupt (SMI)
The SIO10N268 implements a “group” IO_SMI# output pin. The System Management Interrupt is a non-
maskable interrupt with the highest priority level used for OS transparent power management. The nSMI
group interrupt output consists of the enabled interrupts from Super I/O Device Interrupts (Parallel Port,
Serial Ports 1, 2, 3, and 4, and FDC) and many of the GPIOs pins. The GP12/IO_SMI# pin, when selected
for the IO_SMI# function, can be programmed to be active high or active low via bit[2] in the GPIO Polarity
Register 1 (CR32). The IO_SMI# pin function defaults to active low. The output buffer type of the pin can
be programmed to be open-drain or push-pull via GPIO Output Type Register 1 (CR39).
The interrupts are enabled onto the group nSMI output via the SMI Enable Registers 1, 2, and 3. The
nSMI output is then enabled onto the IO_SMI# output pin via bit[7] in the SMI Enable Register 2. The SMI
output can also be enabled onto the serial IRQ stream (IRQ2) via Bit[6] in the SMI Enable Register 2.
8.17.1 SMI Registers
There are six SMI Registers located in the Runtime Register block. They are SMI_EN1, SMI_EN2,
SMI_EN3, SMI_STS1, SMI_STS2, and SMI_STS3. The SMI event bits for the GPIOs events are located
in the SMI status and Enable registers 1 and 2. The polarity of the edge used to set the status bit and
generate an SMI is controlled by the GPIO Polarity Registers located in the Configuration section. For
non-inverted polarity (default) the status bit is set on the low-to-high edge. Status bits for the GPIOs are
cleared on a write of ‘1’.
The SMI logic for the GPIO events is implemented such that the output of the status bit for each event is
combined with the corresponding enable bit in order to generate an SMI.
The SMI event bits for the super I/O devices are located in the SMI status and enable registers 2 and 3.
All of these status bits are cleared at the source; these status bits are not cleared by a write of ‘1’. The SMI
logic for these events is implemented such that each event is directly combined with the corresponding
enable bit in order to generate an SMI.
See Chapter 9 Runtime Registers for the definition of the SMI status and enable registers.
8.18
PME Support
The SIO10N268 offers support for Power Management Events (PMEs), also referred to as System Control
Interrupt (SCI) events in an ACPI system. A power management event is indicated to the chipset via the
assertion of the IO_PME# signal. In the SIO10N268, the IO_PME# is asserted by active transitions on the
ring indicator inputs nRI1, nRI2, nRI3, and nRI4, Watchdog Timer Event (WDT), and programmable edges
on GPIO pins. The nIO_PME pin can be programmed to be active high or active low via bit 5 in the GPIO
Polarity Register 2 (CR34). The nIO_PME pin function defaults to active low, open-drain output. The
output buffer type of the pin can be programmed to be open-drain or push-pull via bit 7 in the GPIO Output
Type Register 2 (CR40). This pin is powered by VTR. See the Configuration section for description on
these registers.
PME functionality is controlled by the PME status and enable registers in the runtime registers block, which
is located at the address programmed in register 0x30 in the Configuration section. The PME Enable bit,
PME_EN, globally controls PME Wake-up events. When PME_EN is inactive, the IO_PME# signal can
not be asserted. When PME_EN is asserted, any wake source whose individual PME Wake Enable
register bit is asserted can cause IO_PME# to become asserted.