H8-Z80-64 (Rev 1.8, Les Bird, 2009)

[pbi...@gmail.com]

Does anyone have a schematic for this board?  It’s not in the documentation at: https://sebhc.github.io/sebhc/pcbs/pcbs.html

 

(I have the board, it’s populated, I’d like to try to use it.  But I’d like to know more than the H8-Z80-64_doc.pdf specifies :->.)

 

Also, at that site this board is described as “This PCB has been replaced by the Rev 2 board”, however I don’t see any information about the follow-on anywhere,  Maybe v1.8 remains current?  Maybe what was meant is the Rev 2.1 GIDE board (https://sebhc.github.io/sebhc/HeathkitGIDE.html) and its successors?

 

-----

paul

 

 

[Les Bird]

Paul,

No schematic exists for the 1.8 or the 2.x boards. They were wired up in KiCad and printed and debugged on the fly. However, most of it is based on existing Heathkit schematics. For example the interfacing circuitry was taken from the 8080 CPU board schematic. On the 2.x boards the area with the HA-8-8 Extended Configuration board was wired up exactly from the original schematic.

And yes the Rev 2 GIDE boards replace the 1.8 boards and by Rev 2 I mean 2.x (2.0, 2.1, 2.2, etc). Norberto has taken the design to a whole new level with the V3 and V4 CPU boards which are now considered the current design.

Les

[pbi...@gmail.com]

Thank you Les; that explains much :->.  Do you perhaps have an unemployed PCB for your rendition of the Extended Configuration board?

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[Les Bird]

Paul,

I will look for Extended Configuration PCBs. Will let you know if I find any. I think I might have some buried away in a box somewhere.

Les

[Glenn Roberts]

I may have an unbuilt PCB as well. On travel now but can check next week if Les doesn’t turn any up.  I don’t do much with 8080 systems except for demos of “early” configurations like I did at VCF so don’t have much call for this board.  The Z80 boards all incorporate this capability as part of their design of course…

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[Glenn Roberts]

Paul: what “more” is it that you’re looking for?  Have you not been able to get this board to work? Maybe if you shared more info we could help. From the 1.8 through the various 2.x improvements all the boards share a common lineage.  I run the 2.6 in Rusty.

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[pbi...@gmail.com]

Thank you Les.  Your investment in time won’t go unappreciated :->.

 

From: se...@googlegroups.com <se...@googlegroups.com> On Behalf Of Les Bird

Sent: Friday, November 26, 2021 1:37 PM
To: SEBHC <se...@googlegroups.com>

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[pbi...@gmail.com]

Thank you Glenn.  Yes, “why is he asking all of these questions about a ‘legacy’ configuration” :-}?  Well in part because my microprocessor “origin story” starts with a TDL ZPU (2 MHz) with a pair of half-populated WMC MEM-3 SRAM boards (so 32K total) on an S100 backplane in an Integrand case and an H19 terminal circa 1979.  So I’m using the H8 to explore hands-on a bit earlier than that (ca. 1977).

 

WRT Cassette I/O I’ve been eyeing building one of these for use stand-alone:

 

https://www.sites.google.com/site/tedrossin/home/electronics/pic#h.atweos91tg81

 

However it would be useful to build a piggyback board to non-destructively repurpose the cassette I/O UART to a “fileserver” purpose at times.

[pbi...@gmail.com]

Glenn:  Just in “look before you leap” mode!  Les has provided a basic explanation of his design intent(s) in the v1.8 board, which definitely helps.  Frank Madison has explained his modifications to the “stock” board, but design aspects of the v1.8 board pre-mod aren’t documented anywhere and it would be “mighty nice” to understand those better before I engage in any card-swapping.  For example, I see a connector to cable to the front panel, but what functionality does that support (given a Z80) compared to the 8080 CPU board?  It appears from Les’ documentation that the IE LED gets driven; is that it?

 

Anyway, if there are no schematics then there are no schematics.  Taking this backwards, what is the earliest board in the series (leading eventually to V4, as I understand it) that has a published schematic?  I imagine that there’s been a lot of design-conservation involved.

 

I’m generally more interested in the HW angle than the SW angle at this stage.  E.g., there are lots of means to run CP/M out there if that were the only point to this exercise  :->.

 

From: se...@googlegroups.com <se...@googlegroups.com> On Behalf Of Glenn Roberts
Sent: Friday, November 26, 2021 9:18 PM
To: se...@googlegroups.com

Subject: Re: [sebhc] H8-Z80-64 (Rev 1.8, Les Bird, 2009)