User Guide • SC5-FESTIVAL • CompactPCI
®
Serial CPU Board
Main Power Supply Control (PS_ON#)
The SC5-FESTIVAL draws its power from the +12V main supply rail defined by the
CompactPCI
®
Serial
specification. The board has been designed to control this main power supply by use of the signal
PS_ON# (connector P1 pin E2). If the system enters the sleep state S5 (soft off), the signal PS_ON#
is pulled high, hence the main power supply is switched-off. The SC5-FESTIVAL is held in soft off state
until a power management event (e.g. power button event triggered by the front panel handle) brings
back the system to the S0 state.
In order to work as described above and to generate clean signals on PS_ON#, the stand-by voltage
+5VSTB is necessary. This optional power rail, tied to connector P1 pin B1, is also part of the
CompactPCI
®
Serial specification. The stand-by power rail must be switched-on “always”, independent
of the state of PS_ON#.
Nevertheless, +5VSTB is not mandatory to operate the SC5-FESTIVAL. If no stand-by power is
available, the board creates this voltage from the main power rail. In this case it is important that the
PS_ON# signal is pulled down somewhere in the system.
Power Supply Status (PWR_FAIL#)
Power supply failures may be detected before the system crashes down by monitoring the signal
PWR_FAIL#. This active low line (connector P1 pin F3) is an addition to the
CompactPCI
®
Serial
specification and may be driven by the power supply. PWR_FAIL# signals the possible failure of the
main supply v12V. On the SC5-FESTIVAL the signal PWR_FAIL# is routed to GPP_D0 of the
CM238 PCH to analyse the state of the power supply unit.
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