Subject:
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more address lines on expansion board
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 8 Apr 1996 04:04:26 GMT
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Original-From:
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Randy Sargent <rsargent@newtonlabs.NOSPAMcom>
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Viewed:
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1779 times
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Hi Brian,
When Fred and I designed the Rev 2.0 6.270 controller, we consciously made
the expansion bus small and simple. For most expansion devices, the
pre-decoded chip selects make more sense than sending all the address
lines, since the latter requires a bigger connector and an external chip to
decode the address lines (in most cases).
However, we realized that some folks would want more address lines. Rather
than make a big, klunky connector for the very small percentage of people
who'd need this, we consciously placed the RAM an even .1" multiple from
the expansion connector. This is so that you could take the RAM out of the
board, put a wire-wrap socket in your expansion board (whose pins now plug
in where the RAM used to be), and then re-plug in the RAM in the WW socket
on your expansion board. It's a little klunky, but you now have
demultiplexed address lines.
Although the Handyboard is very similar to the 6.270 board, I'm not sure if
it sticks to the same spacing constraint (it's only important if you're
doing a proto board, though, not a PC board).
Hope this helps.
-- Randy
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