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User’s Guide 21020285 D
Chapter 3 Hardware Installation
Step 2: Jumpers and Termination Page 3 - 7
Bus Request/
Grant Jumper
This jumper block is used to select the level at which the RF3880 adapter can
request and be granted access to the VMEbus by the ARBITER. The four sets
of Bus Request and Grant signals are daisy-chained separately on the VMEbus
backplane. Only one of the four levels can be used by a single REQUESTER.
The Bus Grant signals that are not used are passed through to the next board
on the backplane. The Bus Grant signal will be gated on the adapter for
whichever level you choose. If the RF3880 adapter has a request for the bus
pending, it will take control of the VMEbus. If it has no request pending it will
pass the Bus Grant signal to the next board. The Bus Request/Grant jumper
block is illustrated below.
Figure 5 Bus Request/Grant and Sysfail Jumpers
The setting shown in the above figure is the default from the factory. It indicates
level 3 for Bus Request/Grant.
To select a Bus Request/Grant level, place three jumpers down the level you
wish to use. The unused levels should have jumpers placed from pin 4 to 5.
Figure 6 Bus Request and Grant on Level 2
Figure 7 Bus Request and Grant on Level 1