Pentium
II Processor at 350 MHz, 400 MHz, and 450 MHz
Datasheet
79
PWRGOOD
I
The PWRGOOD (Power Good) signal is a 2.5 V tolerant processor input. The processor
requires this signal to be a clean indication that the clocks and power supplies (V
CC
,
etc.) are stable and within their specifications. Clean implies that the signal will remain low
(capable of sinking leakage current), without glitches, from the time that the power supplies
are turned on until they come within specification. The signal must then transition
monotonically to a high (2.5 V) state. The figure below illustrates the relationship of
PWRGOOD to other system signals. PWRGOOD can be driven inactive at any time, but
clocks and power must again be stable before a subsequent rising edge of PWRGOOD. It
must also meet the minimum pulse width specification in
Table 14
and
Table 15
, and be
followed by a 1 ms RESET# pulse.
The PWRGOOD signal must be supplied to the processor; it is used to protect internal
circuits against voltage sequencing issues. It should be driven high throughout boundary
scan operation.
PWRGOOD Relationship at Power-On
REQ[4:0]#
I/O
The REQ[4:0]# (Request Command) signals must connect the appropriate pins of all
Pentium II processor system bus agents. They are asserted by the current bus owner over
two clock cycles to define the currently active transaction type.
RESET#
I
Asserting the RESET# signal resets all processors to known states and invalidates their L1
and L2 caches without writing back any of their contents. RESET# must remain active for
one microsecond for a “warm” Reset; for a power-on Reset, RESET# must stay active for at
least one millisecond after V
CC
and CLK have reached their proper specifications. On
observing active RESET#, all Pentium II processor system bus agents will deassert their
outputs within two clocks.
A number of bus signals are sampled at the active-to-inactive transition of RESET# for
power-on configuration. These configuration options are described in the
P6 Family of
Processors Hardware Developer’s Manual
(Order Number 244001) for details.
The processor may have its outputs tristated via power-on configuration. Otherwise, if
INIT# is sampled active during the active-to-inactive transition of RESET#, the processor
will execute its Built-in Self-Test (BIST). Whether or not BIST is executed, the processor
will begin program execution at the power on Reset vector (default 0_FFFF_FFF0h).
RESET# must connect the appropriate pins of all Pentium II processor system bus agents.
RP#
I/O
The RP# (Request Parity) signal is driven by the request initiator, and provides parity
protection on ADS# and REQ[4:0]#. It must connect the appropriate pins of all Pentium II
processor system bus agents.
A correct parity signal is high if an even number of covered signals are low and low if an
odd number of covered signals are low. This definition allows parity to be high when all
covered signals are high.
RS[2:0]#
I
The RS[2:0]# (Response Status) signals are driven by the response agent (the agent
responsible for completion of the current transaction), and must connect the appropriate
pins of all Pentium II processor system bus agents.
Table 41. Signal Description (Sheet 6 of 8)
Name
Type
Description
BCLK
PWRGOOD
RESET#
D0026-00
1 msec
V
IH,mn
V
CC
,
V
CCP
,
V
REF