Motorola MCPN750A, Installation And Use Manual

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Functional Description
6
Hot Swap Control Circuitry
The MCPN750A provides CompactPCI Hot Swap capability and complies
with the CompactPCI Hot Swap Specification (Rev. 1.0). The Hot Swap
circuitry supports the process of installing or removing the board without
adversely effecting the running system.
The Hot Swap circuitry consists of the Linear Technology LTC1643
controller along with some external FETs and discrete components. The
two external N-channel FETs control the +5V and +3.3V supplies while
on-chip switches control the +12V and -12V supplies. All supply voltages
are increased at a controlled rate. An electronic circuit breaker protects all
four supplies against over-current faults.
A switch, located in the lower ejector handle, is used to signal the insertion
or impending removal of the board. The state of this switch is monitored
by the 21554 bridge chip which will assert the CompactPCI ENUM#
signal. The ENUM# signal indicates to the System Controller board either
that the board has been inserted and is ready for configuration or that the
board is about to be removed. A blue LED is provided on the front panel
to indicate when it is safe to remove the board from the chassis.
Programmable Timers
Among the resources available to the local processor are a number of
programmable timers. Timers and counters on the MCPN750A are
provided by the Raven ASIC, the M48T559 and, the PBC . They can be
programmed to generate periodic interrupts to the processor.
Raven General Purpose Timers
The Raven ASIC contains four 31-bit general purpose timers. Each timer
is driven by a divide-by-eight prescaler which is synchronized to the PPC
processor clock. For a 66.66 MHz system, the timer frequency would be
8.25 MHz. Each timer may be programmed to generate an MPIC interrupt.