Signal Description
2-8
Intel
82801BA ICH2 Datasheet
2.11
Processor Interface
Table 2-11. Processor Interface Signals
Name
Type
Description
A20M#
O
Mask A20:
A20M# will go active based on either setting the appropriate bit in the
Port 92h register, or based on the A20GATE input being active.
Speed Strap:
During the reset sequence, ICH2 drives A20M# high if the
corresponding bit is set in the FREQ_STRP register.
CPUSLP#
O
Processor Sleep:
This signal puts the processor into a state that saves
substantial power compared to Stop-Grant state. However, during that time, no
snoops occur. The ICH2 can optionally assert the CPUSLP# signal when going to
the S1 state.
FERR#
I
Numeric Coprocessor Error:
This signal is tied to the coprocessor error signal
on the processor. FERR# is only used if the ICH2 coprocessor error reporting
function is enabled in the General Control Register (Device 31:Function 0, Offset
D0, bit 13). If FERR# is asserted, the ICH2 generates an internal IRQ13 to its
interrupt controller unit. It is also used to gate the IGNNE# signal to ensure that
IGNNE# is not asserted to the processor unless FERR# is active. FERR# requires
an external weak pull-up to ensure a high level when the coprocessor error
function is disabled.
IGNNE#
O
Ignore Numeric Error:
This signal is connected to the ignore error pin on the
processor. IGNNE# is only used if the ICH2 coprocessor error reporting function is
enabled in the General Control Register (Device 31:Function 0, Offset D0,
bit 13). If FERR# is active, indicating a coprocessor error, a write to the
Coprocessor Error Register (F0h) causes the IGNNE# to be asserted. IGNNE#
remains asserted until FERR# is negated. If FERR# is not asserted when the
Coprocessor Error Register is written, the IGNNE# signal is not asserted.
Speed Strap:
During the reset sequence, ICH2 drives IGNNE# high if the
corresponding bit is set in the FREQ_STRP register.
INIT#
O
Initialization:
INIT# is asserted by the ICH2 for 16 PCI clocks to reset the
processor. ICH2 can be configured to support processor BIST. In that case, INIT#
will be active when PCIRST# is active.
INTR
O
Processor Interrupt:
INTR is asserted by the ICH2 to signal the processor that
an interrupt request is pending and needs to be serviced. It is an asynchronous
output and normally driven low.
Speed Strap:
During the reset sequence, ICH2 drives INTR high if the
corresponding bit is set in the FREQ_STRP register.
NMI
O
Non-Maskable Interrupt:
NMI is used to force a non-maskable interrupt to the
processor. The ICH2 can generate an NMI when either SERR# or IOCHK# is
asserted. The processor detects an NMI when it detects a rising edge on NMI.
NMI is reset by setting the corresponding NMI source enable/disable bit in the NMI
Status and Control Register.
Speed Strap:
During the reset sequence, ICH2 drives NMI high if the
corresponding bit is set in the FREQ_STRP register.
SMI#
O
System Management Interrupt:
SMI# is an active low output synchronous to
PCICLK. It is asserted by the ICH2 in response to one of many enabled hardware
or software events.
STPCLK#
O
Stop Clock Request:
STPCLK# is an active low output synchronous to PCICLK.
It is asserted by the ICH2 in response to one of many hardware or software
events. When the processor samples STPCLK# asserted, it responds by stopping
its internal clock.
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