E
ISA Bus. PIIX4 contains 14 separate device monitors, each capable of detecting activity for a different type of
device. Figure 14 illustrates the logic associated with each device monitor.
82371AB (PIIX4)
211
4/9/97 2:23 PM PIIX4aDS
INTEL CONFIDENTIAL
(until publication date)
PRELIMINARY
Device
Access
(I/O, Mem)
DACK#
GPI
Idle Timer
(for each device)
Trap
(for each device)
Re-Load
SMI#
Global Timer Re-Load
Clock Break/Burst Timer Reload
Forward Cycle to EIO Bus
[Idle Status]
To Clock Control
[Trap Status]
(With/DEVSEL# for I/O Re-Start)
SMI#
dev_mon
Figure 14. Device Monitoring Logic
11.3.1.
DEVICE IDLE TIMER
Each Device has an Idle Timer (except Device 12 and 13) that can be reloaded by activity on that device.
Individual device monitors are configured to monitor a specific type of device, such as an IDE hard drive or the
audio subsystem. Activity indication is specific to each device and can include the following:
Device Access.
Specific I/O or Memory ranges associated with that device are monitored on the PCI bus.
Most devices have multiple options to allow for a wide range of system configurations.
DMA Acknowledge.
DACK# used for DMA transfers by the device, if applicable (Audio, Floppy, LPT).
General Purpose Input.
Most device monitor can watch for assertion of a specific General Purpose Input
(GPI) pin. Each GPI signal can have its assertion polarity modified to be high or low. Two GPI signals
(device 12 and 13) can also be enabled for edge transition detection.
System Activity.
Miscellaneous activity such as Keyboard or Mouse interrupt, PCI bus Master activity, or
PCI bus utilization (used to monitor for graphics activity) may be monitored for specific devices.
A device access, DACK# assertion, or GPI signal can be enabled to reload the device’s Idle Timer as well as to
reload the Global Standby Timer or the Fast Burst or Slow Burst Timers.
Some of the device monitors can serve multiple functions. For example, the Device 3 IDE Secondary IDE Drive
1 monitor can also be enabled as a programmable Software Timer. The Device 8 LPT monitor can be enabled to
monitor parallel port activity or PCI Bus Master activity.
When the Idle Timer expires (due to no reload activity), an Idle Status bit is set and an SMI# is generated if
enabled. The power management software can then place the idle device into a power managed condition. The
idle timers stop counting when the [SM_FREEZE] bit is set. This can be used to keep the idle timers from
counting down when the system is executing an SMI routine.