
LPC Interface Bridge Registers (D31:F0)
8-72
82801AA and 82801AB Datasheet
8.9.7
TCO2_STS—TCO2 Status Register
I/O Address:
Default Value:
Lockable:
TCOBASE +06h
0000h
No
Attribute:
Size:
Power Well:
R/W
16 bits
Resume
(Except Bit 0, in RTC)
8
BIOSWR_STS
.
1= ICH sets this bit and generates and SMI# to indicate an illegal attempt to write to the BIOS. This
occurs when either: a) The BIOSWE bit is changed from 0 to 1 and the BLD bit is also set, or b)
any write is attempted to the BIOS and the BIOSWE bit is also set.
NOTE:
On write cycles attempted to the 4 MB lower alias to the BIOS space, the BIOSWR_STS is
not set.
7
NEWCENTURY_STS.
This bit is in the RTC well.
1 = This bit is set to 1 when the Year byte (RTC I/O space, index offset 09h) rolls over from 99 to 00.
Setting this bit causes an SMI# (but not a wake event).
0 = Cleared by writing a 1 to the bit position or by RTCRST# going active.
6:4
Reserved
3
TIMEOUT.
Bit set to 1 by ICH to indicate that the SMI was caused by the TCO timer reaching 0.
2
TCO_INT_STS.
1 = SMI handler caused the interrupt by writing to the TCO_DAT_OUT register.
1
SW_TCO_SMI.
1 = Software caused an SMI# by writing to the TCO_DAT_IN register.
0
NMI2SMI_STS.
1 = Set by the ICH when an SMI# occurs because an event occured that would otherwise have
caused an NMI.
0 = Cleared by writing a 1 to this bit position.
Bit
Description
Bit
Description
15:3
Reserved
2
BOOT_STS.
1 = Set to 1 when the SECOND_TO_STS bit goes from 0 to 1 and the processor has not fetched the
first instruction.
0 = Cleared by ICH based on RSMRST# or by software writing a 1 to this bit. Note that software
should first clear the SECOND_TO_STS bit before writing a 1 to clear the BOOT_STS bit.
NOTE:
If rebooting due to a second TCO timer timeout, and if the BOOT_STS bit is set, the ICH will
reboot using the ‘safe’ multiplier (1111). This allows the system to recover from a processor
frequency multiplier that is too high, and allows the BIOS to check the BOOT_STS bit at boot.
If the bit is set and the frequency multiplier is 1111, then the BIOS knows that the processor
has been programmed to an illegal multiplier.
1
SECOND_TO_STS.
1 = The ICH sets this bit to a 1 to indicate that the TCO timer timed out a second time (probably due to
system lock). If this bit is set the ICH will reboot the system after the second timeout. The reboot is
done by asserting PCIRST#.
0 = This bit is cleared by writing a 1 to the bit position or by a RSMRST#.
0
Intruder Detect (INTRD_DET).
This bit is in the RTC well.
1 = Set by ICH to indicate that an intrusion was detected. This bit is set even if the system is in G3
state.
0 = This bit is only cleared by writing a 1 to the bit position or by RTCRST#.