What is the purpose of the 5V AUX jumper on PICMG 1.3 backplanes and can the SHB be inserted or removed with the incoming AC voltage to the power supply still on?
The PICMG 1.3 specification requires that voltage be applied to the SHB’s 5V standby (or auxiliary) pins. If a power supply does not provide 5V AUX, the CPU will not properly power on. Normally this 5V AUX jumper is used to route 5V AUX to the CPU board. For power supplies without 5V AUX, this jumper routes regular 5V to the SHB’s 5V AUX pins. A PICMG 1.3 SHB should not be removed from the backplane slot with the incoming AC power turned on. Even if the power supply has been turned off by an orderly soft-control shutdown, the 5V standby voltage will remain active until the incoming AC to the system power supply has been turned off or unplugged. This is why most PICMG 1.3 backplanes have a 5V AUX LED indicator. When the 5V AUX LED is off, this is your indication that it is safe to remove the PICMG 1.3 SHB from the backplane.
