Andrew Bingham
2014-01-20 23:49:24 UTC
All,
I'm starting my ECB bus build in a Siemens/TI 505-6508 chassis; I'll be
using one of the 12-slot backplanes that John C. has designed specifically
for that chassis.
As part of that build, I've realized there are a few drawbacks to the
existing Bus Monitor board:
1. The existing card only supports 16-bit addresses and 8-bit data. The
mini-68k CPU board drives up to 22-bit address, and 24-bit is a clear
possibility. 16-bit data is a future possibility as well. (The available
CPU and memory cards have, happily, outgrown the original Bus Monitor.)
2. If displays/DIP switches are installed in the current card and it is
installed inside a chassis with other cards near it, the displays/DIP
switches are not easily visible/accessible - the card is really best suited
for use in a benchtop open air chassis. (With surplus prices of the
505-6805 dropping, we now have an excellent off-the-shelf chassis available
with a backplane to match)
3. Connecting external LEDs requires hard-to-locate or custom cables ending
in DIP20 package-like connections. (this makes it difficult to resolve #2
above)
I'm starting work on an update to the Bus Monitor card that will address
some of these issues. I'd like to get input from the group as to any
features that would be desirable in such an update. Right now I have the
following *minimum set* of changes identified. I would consider this the
"Extended Bus Monitor" - it is a minimum set of changes that extend the
existing design and fix drawback #1 above, but #2 & #3 remain.
1. Expand address lines to 24-bit and data lines to 16-bit. Add /DS0 and
/DS1 (high and low byte transfer signals) to monitored signals. Update
layout to try and fit these new items (1 DIP8, 2 10-segment bar graphs)
onto the PCB. The current board is pretty full so it's not clear
everything will fit.
A more extensive set of changes would product what I would call the "Bus
Monitor V2":
1. Expand address lines to 24-bit and data lines to 16-bit. Add /DS0 and
/DS1 (high and low byte transfer signals) to monitored signals.
2. Move the LED displays and DIP switches onto a Front Panel/daughterboard
connected with standard headers. This would free up additional space on
the Bus Monitor PCB itself, as well as allowing for multiple display/front
panel configurations similar to the S-100 Bus Monitor/Front Panel
combination which has 3 options for the front panel part.
So, questions for the group:
-Which approach above makes the most sense? Extended or V2?
-Is there interest from the ~5 people who are building systems in the
505-6508 chassis in having a new Bus Monitor to use with their builds? From
others?
*-Are there any other new signals, for instance used by the SBC-188, SBC
Mark IV, mini-68k, etc that would be useful to include in a revision of the
Bus Monitor?*
I've already taken an initial stab at a schematic for the Extended version
but haven't made it to trying to route the PCB yet.
(In my head I have an image of a sweet "modernized" front panel with a
Propeller or another microcontroller driving an LCD or VFD multiline
character display and 4 buttons with a menu to setup which addresses to
latch the display on, etc....but that's a whole separate project on its own
that doing the V2 option would enable if all the LED and switches were on a
separate card.)
Thanks,
Andrew
I'm starting my ECB bus build in a Siemens/TI 505-6508 chassis; I'll be
using one of the 12-slot backplanes that John C. has designed specifically
for that chassis.
As part of that build, I've realized there are a few drawbacks to the
existing Bus Monitor board:
1. The existing card only supports 16-bit addresses and 8-bit data. The
mini-68k CPU board drives up to 22-bit address, and 24-bit is a clear
possibility. 16-bit data is a future possibility as well. (The available
CPU and memory cards have, happily, outgrown the original Bus Monitor.)
2. If displays/DIP switches are installed in the current card and it is
installed inside a chassis with other cards near it, the displays/DIP
switches are not easily visible/accessible - the card is really best suited
for use in a benchtop open air chassis. (With surplus prices of the
505-6805 dropping, we now have an excellent off-the-shelf chassis available
with a backplane to match)
3. Connecting external LEDs requires hard-to-locate or custom cables ending
in DIP20 package-like connections. (this makes it difficult to resolve #2
above)
I'm starting work on an update to the Bus Monitor card that will address
some of these issues. I'd like to get input from the group as to any
features that would be desirable in such an update. Right now I have the
following *minimum set* of changes identified. I would consider this the
"Extended Bus Monitor" - it is a minimum set of changes that extend the
existing design and fix drawback #1 above, but #2 & #3 remain.
1. Expand address lines to 24-bit and data lines to 16-bit. Add /DS0 and
/DS1 (high and low byte transfer signals) to monitored signals. Update
layout to try and fit these new items (1 DIP8, 2 10-segment bar graphs)
onto the PCB. The current board is pretty full so it's not clear
everything will fit.
A more extensive set of changes would product what I would call the "Bus
Monitor V2":
1. Expand address lines to 24-bit and data lines to 16-bit. Add /DS0 and
/DS1 (high and low byte transfer signals) to monitored signals.
2. Move the LED displays and DIP switches onto a Front Panel/daughterboard
connected with standard headers. This would free up additional space on
the Bus Monitor PCB itself, as well as allowing for multiple display/front
panel configurations similar to the S-100 Bus Monitor/Front Panel
combination which has 3 options for the front panel part.
So, questions for the group:
-Which approach above makes the most sense? Extended or V2?
-Is there interest from the ~5 people who are building systems in the
505-6508 chassis in having a new Bus Monitor to use with their builds? From
others?
*-Are there any other new signals, for instance used by the SBC-188, SBC
Mark IV, mini-68k, etc that would be useful to include in a revision of the
Bus Monitor?*
I've already taken an initial stab at a schematic for the Extended version
but haven't made it to trying to route the PCB yet.
(In my head I have an image of a sweet "modernized" front panel with a
Propeller or another microcontroller driving an LCD or VFD multiline
character display and 4 buttons with a menu to setup which addresses to
latch the display on, etc....but that's a whole separate project on its own
that doing the V2 option would enable if all the LED and switches were on a
separate card.)
Thanks,
Andrew
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