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Hardware Preparation and Installation
2
2-16
firmware. This may be changed, by software, to any other base
address. Refer to the Single Board Computers Programmer's Reference
Guide for details.
If the MVME177 attempts to access offboard resources in a
nonexistent location, and is not system controller, and if the system
does not have a global bus time-out, the MVME177 waits forever for
the VMEbus cycle to complete. This causes the system to hang up.
There is only one situation in which the system might lack this
global bus time-out:
The MVME177 is not the system controller, and
There is no global bus time-out elsewhere in the system
Multiple MVME177 modules may be configured into a single VME
card cage. In general, hardware multiprocessor features are
supported.
Other MPUs on the VMEbus can:
Interrupt
Disable
Communicate with, and
Determine the operational status of
the processor(s). One register of the GCSR set includes four bits
which function as location monitors to allow one MVME177
processor to broadcast a signal to other MVME177 processors, if
any. All eight registers are accessible from any local processor as
well as from the VMEbus.
The MVME177 provides +12 Vdc power to the Ethernet LAN
transceiver interface through a 1 amp polyswitch F2 located on the
MVME177 module. The +12V LED lights when +12 Vdc is
available. The polyswitch is located near diode CR1. Polyswitches
act like circuit breakers that reset automatically when the excessive
load is removed. If the Ethernet transceiver fails to operate, check
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