
SiS5595 PCI System I/O Chipset
Preliminary V2.0 Nov. 2, 1998 35 Silicon Integrated Systems Corporation
Upon power up, the three standby timers are frozen which means they keep reloading the
initial count from their associated system timer register (default 00h). Setting "System
Standby Timer X SMI# Enable (bit 31, 30, and 29 of PMU Register 60h-63h) will de-freeze
the system standby timer 0, 1, and 2, respectively. Upon expiration, the corresponding
System Standby Timer X SMI# Request Status Bit is set, and the SMI# is generated. Note
that the standby timer stays at "reloading" status upon expiration.
The SMI# Request Status allows the SMI# routine to identify which SMI# source is coming.
Bit31, 30, and 29 of Register PMU 64h-67h correspond to the SMI# Request Status Bit for
the system standby timer 0, 1, and 2, respectively. Writing a logic 1 to the SMI# Request Bit
clears the status bit, and enables the standby timer count down again if its corresponding
SMI# Enable bit is not cleared. It is recommended to disable the SMI# Enable bit before
programming the initial count to make a clean start, meaning that the standby timer really
counts down starting from the initial count. Before the timer is expired, it can be reloaded if
any of the enabled reload events is identified, and then counts down again.
3.2.2.2 Wake Up Event Recognizers
Two independent Wake Up Event Recognizers are provided to allow the system designers to
flexibly meet the Green PC application. The main mission of the WUER (Wake Up Event
Recognizers) is to generate SMI# upon detecting the wake up events, if the corresponding
SMI# Enable bit is set.
Table 3.2-5 Wakeup Event from PMU
TIMER
RELOAD EVENT
WAKEUP
(PMU)
0
Defined on PMU Configuration Register 50h~53h
The wakeup event is same as System Standby Timer 0 except GPI
[17, 15:7, 5:1].
Defined on PMU Configuration Register 54h~57h
The wakeup event is same as System Standby Timer 0 except GPI
[17, 15:7, 5:1].
WAKEUP
(PMU)
1
To summarize the supported Wake UP Event Set, namely WakeUp0, and WakeUp1 which
can be defined by programming the wake up event control registers locating on 50h-53h and
54h-57h of PMU configuration space, respectively. Bit 28, and 27 of the SMI# Enable
Register enables/disables the generation of SMI# while wake up event is recognized. The
WUER is designed to be quite independent on the system state (Sleep, or Throttling state).
The wake up event can be recognized, and thus SMI# be generated as long as its
corresponding enable bit in the wake event control register is set.
3.2.2.3 SMI# Generation Logic
SiS5595 PMU allows a versatile event that could give rise to the generation of SMI#. Two
sets of registers, namely SMI# Enable Registers, and SMI# Status Register relate to the
SMI# generating logic. The SMI# Enable register locating on Register 60h to 63h enables
the generation of SMI# upon that any of the enabled events is recognized. SMI# Request
Status register, locating on Register 64h to 67h reflects the event(s) producing the SMI#.