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The Software Connection Control resources on the board provide a signal (ENUM#) for
system host notification and a switch and LED to interface with the operator.
Full Hot Swap boards drive the ENUM# signal to the system host to indicate a service
request. This signal is provided to notify the system host that either a board has been
freshly inserted or is about to be extracted. This signal informs the system host that the
configuration of the system has changed. The system host then performs any necessary
maintenance such as installing a device driver upon board insertion, or unloading drivers
for hot swap boards that are about to be extracted. The application that is using the board is
also notified that the resource will no longer be available.
The Hot Swap Switch allows the operator to indicate desire to extract the board. A blue
LED, located on the front of the board, is illuminated when it is safe to extract the board.
This LED indicates that system software has been placed in a state for orderly extraction of
the board. The hardware connection layer provides protection only for the hardware during
insertions and extractions. This method allows the operator to insert or extract boards
without the extra step of reconfiguring the system at the console.
All actions are initiated by the operator, and must be performed in the correct
sequence for proper system operation.
Full Hot Swap boards present the following resources to software executing on the system
host (nominally implementing the Hot-Plug Service and Hot-Plug System Driver)
An ENUM# signal, which is an open collector (open drain) bussed signal, to
signal a change in status for the board.
A switch actuated with the lower ejector handle, indicating the beginning of
the extraction process or end of the insertion process.
A LED to indicate the status of the software connection process.
A set of four control and status bits on each board allows the system host's
software to determine the source of the ENUM# signal and control the LED.
Full Hot Swap boards allow the full range of system capabilities.
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