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PREPARATION FOR USE
2-13.
iSBC 86/14 BOARD RAM ADDRESS CONFIGURATION.
As shipped from the
factory, the iSBC 86/14 board is configured with 32k bytes of RAM at
Multibus addresses 09FFFFH through 098000H.
You can relocate the 32k
bytes of dual port RAM to any 8k ending boundary within any 128k byte
page in the selected megabyte of memory space.
Jumper post
configurations select one of sixteen one-megabyte sections of Multibus
address space in which to reside, select a 128k byte page within the
megabyte, select an 8k ending boundary within the page, and select the
amount of RAM available as a Multibus resource (in increments of 25% of
the total RAM available).
The megabyte selection jumpers (E220, E221, E222, E224) assign the
Multibus address (of the dual port RAM) to one of 16 one-megabyte blocks
of system address space.
Table 2-6 lists the jumpers required for each
of the 16 configurations.
Within the selected megabyte, the Multibus address is further assigned
via jumper posts E225, E226, and E227 to one of 8 possible 128k pages;
that is, you can select one of 8 possible 128k pages for starting the
Multibus address sequence.
Table 2-7 provides the jumper connections
that select the pages.
Within the selected 128k page, you can select any 8k boundary to be the
ending address; that is, you can select one of 16 possible 8k boundaries
within the 128k page at which to end the Multibus address sequence (of
the dual port RAM).
Jumpers E230 through E233 and E240 through E243
provide the selection.
Table 2-8 provides the jumper connections that
select the 8k ending boundaries.
NOTE
You must select the 8k boundary such
that the Multibus address sequence for
the dual port RAM does not increment
across a 128k byte page boundary.
Failure to do so makes the memory
locations beyond the 128k page boundary
inaccessible.
Figure 2-4 provides a Multibus address configuration example for an
iSBC 86/14 board providing 8k bytes of dual port RAM at Multibus address
locations OCBFFFH through OCAOOOH.
2-24
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