2
Hardware Description
39
Table 9
lists
the
potential
sources/triggers
for
the
MR
‐
Reset.
Though
similar,
these
sources
are
slightly
different
from
those
for
a
platform
or
powergood
reset.
Watchdog timers
The
CPM
uses
a
number
of
watchdog
timers
to
prevent
the
board
from
entering
an
unrecoverable
state.
The
IPMC
and
the
IPMC
FPGA
provide
the
following
watchdog
timers:
•
Corrupt
Flash
detection
watchdog
•
OS
watchdog
timer
(Watchdog
1)
•
IPMC
watchdog
timer
(Watchdog
2)
The
following
sections
describe
the
operations
performed
by
each
watchdog.
Corrupt Flash detection watchdog
The
Corrupt
Flash
Detection
(CFD)
Watchdog
is
a
SW
‐
based
watchdog
that
allows
the
CPM
to
recover
when
the
primary
SPI
flash
is
either
blank
or
the
boot
block
is
corrupted.
The
CFD
watchdog
timer
is
started
any
time
that
a
reset
is
asserted
to
the
payload
processor
(for
example,
platform
reset,
push
button
reset,
and
so
on).
Responsibility
is
then
passed
to
the
system
BIOS
to
disable
the
timer.
If
the
timer
is
not
disabled
before
it
expires,
the
IPMC
firmware:
1. Disables
payload
power,
2. Selects
the
secondary
boot
flash
using
the
Boot
Flash
Select
Control,
and
then
3. Re
‐
enables
payload
power
to
boot
from
the
secondary
SPI
flash.
OS watchdog timer (Watchdog 1)
This
programmable
watchdog
is
used
with
the
BIOS
and
the
Linux
OS.
It
can
be
used
by
any
OS.
Table 9. Memory-Retained Reset Sources
Platform Reset Source
Description
Front panel Reset button
(FP_RESET*)
Pushing the button triggers an RCIN* assertion to the PCH, thus beginning the INIT*
sequence.
RTM reset push button
The RTM MMC sends OEM command to IPMC. Upon receiving the “warm reset” OEM
command, the IPMC asserts IPMC_MR_RESET*
IPMC warm reset command
(IPMC_COLD_RESET*)
One of the following two triggers are detected by the IPMC:
• Watchdog timer 1 is configured for warm reset and times out.
• The IPMC warm reset command is recognized.
Once one of the above triggers are detected, the IPMC_MR_RESET* signal is asserted
to the CC FPGA which triggers an RCIN* assertion to the PCH, thus beginning the INIT*
sequence.