[N8VEM: 17117] 20 or 24-bit version of Bus Monitor?

Discussion:

Andrew Bingham

2014-01-13 03:54:37 UTC

Hello,

I'm starting the process of building up an ECB system. I'm planning to use
my Zeta with the Zeta-2-ECB board to start with, and then one of John's
Mark IV Z180 boards when they are debugged, and maybe branch out into the
SBC-188 as well.

I picked up on of the 505-6508 PLC chassis to build in, and I was looking
at making a nice front panel using the Bus Monitor PCB. However I realized
that the SBC-188, mini-68000, and 4MEM boards use (at least) 4 additional
address lines to address up to a full 1 Mb.... From reading the wiki and
the history of the N8VEM project it seems like the Bus Monitor was one of
the first PCBs completed, before the decision was made to extend addressing
to these extra lines.

Are there any thoughts on updating the Bus Monitor to support 20-bit (or
even 24-bit, if the pins are there) addresses for use with the currently
available boards? From a circuit perspective I can see that it would be
simple to do...

Andrew

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John Coffman

2014-01-13 04:10:02 UTC

Permalink

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Andrew:<br>
<br>
    True.  The SBC-188 & 4MEM boards use 20-bit addresses on the
backplane.<br>
<br>
    The Mini-68K uses only 22-bits, but drives all 24 address lines.<br>
<br>
    The Z180 Mark IV has the 20-bit CPU addresses extended to
24-bits on the external bus.  It anticipates a future 24-bit address
width memory board, or can use 4MEM boards either bank switched or
as RAMdisk.<br>
<br>
--John<br>
<br>
<br>
<br>
On 01/12/2014 07:54 PM, Andrew Bingham wrote:
<blockquote
cite="mid:a64553de-132d-4cbb-91a2-103d3ac78d58-/***@public.gmane.org"
type="cite">
<div dir="ltr">Hello,
<div><br>
</div>
<div>I'm starting the process of building up an ECB system.  I'm
planning to use my Zeta with the Zeta-2-ECB board to start
with, and then one of John's Mark IV Z180 boards when they are
debugged, and maybe branch out into the SBC-188 as well.</div>
<div><br>
</div>
<div>I picked up on of the 505-6508 PLC chassis to build in, and
I was looking at making a nice front panel using the Bus
Monitor PCB.  However I realized that the SBC-188, mini-68000,
and 4MEM boards use (at least) 4 additional address lines to
address up to a full 1 Mb....  From reading the wiki and the
history of the N8VEM project it seems like the Bus Monitor was
one of the first PCBs completed, before the decision was made
to extend addressing to these extra lines.</div>
<div><br>
</div>
<div>Are there any thoughts on updating the Bus Monitor to
support 20-bit (or even 24-bit, if the pins are there)
addresses for use with the currently available boards?  From a
circuit perspective I can see that it would be simple to do...</div>
<div><br>
</div>
<div>Andrew</div>
</div>
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Andrew Bingham

2014-01-13 05:33:50 UTC

Permalink

Does anything use data lines above D07? I see that up to D15 are connected
on the backplanes...

True. The SBC-188 & 4MEM boards use 20-bit addresses on the backplane.
The Mini-68K uses only 22-bits, but drives all 24 address lines.
The Z180 Mark IV has the 20-bit CPU addresses extended to 24-bits on
the external bus. It anticipates a future 24-bit address width memory
board, or can use 4MEM boards either bank switched or as RAMdisk.
--John
Hello,
I'm starting the process of building up an ECB system. I'm planning to
use my Zeta with the Zeta-2-ECB board to start with, and then one of John's
Mark IV Z180 boards when they are debugged, and maybe branch out into the
SBC-188 as well.
I picked up on of the 505-6508 PLC chassis to build in, and I was
looking at making a nice front panel using the Bus Monitor PCB. However I
realized that the SBC-188, mini-68000, and 4MEM boards use (at least) 4
additional address lines to address up to a full 1 Mb.... From reading the
wiki and the history of the N8VEM project it seems like the Bus Monitor was
one of the first PCBs completed, before the decision was made to extend
addressing to these extra lines.
Are there any thoughts on updating the Bus Monitor to support 20-bit (or
even 24-bit, if the pins are there) addresses for use with the currently
available boards? From a circuit perspective I can see that it would be
simple to do...
Andrew
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