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2.6
Bus Request and Bus Grant Jumpers
In the Model 4284, jumper blocks JB8, JB9 and JB10 are used for the selection of the
device's VME Bus Request level, and to receive and pass on Bus Grant signals. The
sections below describe the functions of these blocks.
2.6.1
Bus Request Jumpers
The Bus Request signal generated by the Model 4284 is connected to pins 4,
6, 8, and 10 of jumper block JB8. Installing a jumper between pins 3 & 4 of
JB8 connects the internal bus request signal to the VMEbus BREQ0 line,
making the 4284 a level 0 bus requester. Similarly, the 4284 may request
mastership of the VMEbus on level 1 (BREQ1) if a jumper is installed on
JB8 between pins 5 & 6. Placing a jumper between pins 7 & 8 of JB8 allows
the Model 4284 to drive the BREQ2 line as a level 2 requester, and the 4284
can be configured as a level 3 requester (BREQ3) by jumpering pins 9 & 10
of JB8 together (this is the factory default setting).
summarizes jumper settings for JB8.
One, and only one, of the four jumpers described in the table above should
be installed on JB8 at any given time. If two or more of these jumpers are
installed, the VMEbus' priority arbitration scheme is defeated by the
shorting together of bus request lines. If no jumpers are installed, the
4284's VMEbus Master interface is unable to request the bus, effectively
disabling the 4284 as a bus master.
2.6.2
Bus Grant Jumpers
The four VME Bus Grant In signals (BGIn0, BGIn1, BGIn2, and BGIn3) are
connected to pins 1, 3, 5, and 7 of jumper block JB9, respectively. After a
bus requester level has been selected by JB8, the same level's Bus Grant In
signal must be connected to the 4284's VME Master Interface by jumpering
the appropriate odd−numbered pin of JB9 to the adjacent even−numbered
pin. These connections are summarized in
Rev.: F.2
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Table 2−10: Model 4284 VMEbus Master Request and Grant Jumpers
− Jumper Blocks JB8, JB9, and JB10
Bus Request Level Request Pins JB8
BREQ0
BREQ1
BREQ2
*BREQ3
− Jumper Blocks JB9 and JB10
Pe n te k Mo del 4284 Ope rat ing Manual
− Jumper Block JB8
BGIn Pins JB9
3 − 4
1 − 2
5 − 6
3 − 4
7 − 8
5 − 6
9 − 10
7 − 8
* − Factory Default Setting
Table
Table
2−10, below,
BGOut Pins JB10
1 − 2
3 − 4
5 −6
7 − 8
2−10, above.
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