Another H8 saved

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Mike Ladwig

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Aug 29, 2021, 5:36:41 PMAug 29
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The mouse-urine-soaked with exploded tantalums H-8 I bought back in June is now fully functional as I got the H-8-5 serial board working this weekend. Front panel, DG-32 memory board tests out good, cassette interface works well, and the serial console is fully functional! Thank you to the great folks here that offered answers and advice.

A few thoughts:
- The original tantalums are a ticking time bomb. Underspeced when new and not getting better with age
- I replaced a bad 7-segment FND-500 with one from eBay seller mistersprockets1 -- worked and looks perfect
- Some of the Intel 8080 support chips are getting real scarce

Some questions:
- I have two Heathkit H8 8k memory boards without 4044 chips (not a single one survived the mice). Anyone know of a good source for them? Not sure I need more than the 32k memory I already have working, but it would be nice to restore the whole system
- I downloaded a repository of tape software (HUG?) in .wav form. Unfortunately I don't have Basic, the console monitor, text editor, etc. I find lots of related links and references (some of which point to unmirrored parts of the lesbird site, others to the old Norby site, etc.) in the archives but those seem to all be dead
- I found an archive or two of tape software in .H8T form but can't seem to find software to convert them to .wav form although I've seen posts from people who have done it with a utility called H8T that I can't seem to locate

Thanks all!
mike.

Glenn Roberts

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Aug 29, 2021, 9:23:54 PMAug 29
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Mike: great progress!

 

Your best bet at getting software working is to use the H8T files.  I believe it’s possible to use the .WAV files and (say) an iphone, but H8Ts are solid.  They are exact digital images of the contents of the tapes – think of this as what would be captured off the UART when playing back a tape.  The software you need to read them you already have – it’s built into the PAM8 monitor!

 

I do this using an adapter that I built using Dave Runkle’s instructions here:

http://www.astrorat.com/heathkit/heathkith8computer.html

 

but I believe you do not need to build the adapter as you can simply flip the switch on the H-8-5 board, effectively swapping the roles of the two UARTs.  You can then attach a laptop or PC running a terminal emulator program and download the code.  Dave has great instructions on his site (URL above).

 

It is useful to have the Heathkit software reference for the tape version.  I’m not sure this is available in scanned form on any of our sites (?) but I have a paper copy and can provide help.

 

If you are not successful double back here and report on your progress and problems.  I have routinely been able to reliably load the H8T images.  I plan to demo this at VCF East in October…

 

When I finally get back to writing REMarks this would make a good one to write up!

 

  • Glenn

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Mike Ladwig

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Aug 30, 2021, 10:46:05 PMAug 30
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I followed your suggestion and used the H-8-5 switch and had no problems loading H8T files that way -- BHBasic, some tests, etc. -- THANK YOU! Ultimately, I'd like to save that software as .wav files and use some flavor of digital audio to replace the cassette. My goal is to preserve this as an original system for the long term.

I spent a few hours looking for reference manuals for the tape versions of the key software (basic, monitor, assembler, editor) with no luck. I think you are right and they aren't available scanned. Any help you can offer would be greatly appreciated!

mike.

Glenn Roberts

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Aug 31, 2021, 4:48:29 AMAug 31
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Mike: I will scan what I have and share on Les’ site. It’s an important manual since it documents the tape format and some other aspects of using the cassette environment, much of which is non intuitive. If you come up with a reliable way to use a tablet or laptop and .WAV files in lieu of a cassette player it would be great to document that! Maybe do a video!

I have volumes I thru IV of the early HUG  software, which was initially published only a in paper copy form but later as tapes. It is mostly BASIC programs. There exists a Volume V which I don’t have. It would be great to capture these in both analog (.WAV) and digital (.H8T) formats. There is also a HUG package that lets you run these from HDOS, though they clobber the OS since they load at 040.100. David Troendle and I spent a little energy trying to scan and capture these paper listings with mixed results. We put that on hold due to the time and effort required and uncertainty of level of interest.

If you come up with a reliable way to read and preserve these old tape images that would be great! I’m sure some of us would donate old tapes for the purpose of preserving their contents before they’re lost forever.

I wrote a program to convert .ABS format files to .H8T. This lets you use HDOS to assemble your code and then run it on a diskless system by loading from the front panel. This didn’t exist because it only makes sense from a preservationist’s perspective.

Glad you’re preserving the “early days” setup and looking forward to hearing more!

Sent from my iPad

On Aug 30, 2021, at 10:46 PM, Mike Ladwig <mdla...@gmail.com> wrote:

I followed your suggestion and used the H-8-5 switch and had no problems loading H8T files that way -- BHBasic, some tests, etc. -- THANK YOU! Ultimately, I'd like to save that software as .wav files and use some flavor of digital audio to replace the cassette. My goal is to preserve this as an original system for the long term.

Glenn Roberts

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Aug 31, 2021, 10:00:14 PMAug 31
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Mike: To get you started I’ve scanned Chapter 0 of the documentation, which has most of the basics.  The other chapters cover the individual products (edit, dbug, asm, basic, etc) and are fairly similar to their HDOS equivalents.  I’ll scan more and at some point put these on Les’ site…

 

For now it’s in my Google drive:

https://drive.google.com/file/d/1YSm4ZHRoaYu3dnLHDFiza-ULI8Mj-HaG/view?usp=sharing

 

let me know how things go!

Mike Ladwig

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Sep 1, 2021, 9:45:12 PMSep 1
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This is great, thank you! I had started to look at the HDOS version documentation, but I'll wait for your scans.

glenn.f...@gmail.com

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Sep 2, 2021, 7:33:09 AMSep 2
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Ok great. I’ll get those soon.  They go quickly.

 

In order to demonstrate BASIC I am hoping to be able to save and reload programs using the front panel.  Unfortunately haven’t gotten that to work. When I issue the “DUMP” command and capture the serial output I get only the first record (label record). At this point BASIC just loops in a wait state… but waiting for what?  What’s the handshaking model with the cassette drive? (and how can there actually be any since it’s a “dumb” device??)

 

So I used RTM/0 to interrupt and found the code is executing the following:

 

111.232  333 377      WAIT:IN 371     ; Cassette control port

111.234  247               ANA A      ; test bits

111.235  372 232 111       JM WAIT    ; loop ‘til bit 8 clear

 

The AF register shows 205 202.

 

I believe the 8251 is being operated in synchronous mode?  It is looping waiting for the high bit of the control port to be cleared.  Waiting for a SYNC character?  There’s discussion of the 8251 synchronous mode in the H-8-5 manual. Reading through that…

 

Anyway I’m still trying to understand how the handshaking works with cassette use.. any enlightenment would be welcome!

Mike Ladwig

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Sep 2, 2021, 2:18:43 PMSep 2
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I've been able to load the Basic interpreter using the front panel Load command, and Basic programs themselves from inside Basic using the basic command line.

AFAIK, the front panel Load loads the next valid audio file and the Basic interpreter load looks for a file label matching what you tell it on the command line.

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glenn.f...@gmail.com

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Sep 2, 2021, 4:56:42 PMSep 2
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Thanks Mike. My problem was actually a hardware one.  The software was waiting for the DSR line to go high.  On the H-8-5 board there’s actually a little 5 second timer that holds DSR low while the tape motor spins up (which also provides a nice gap between files on the tape). For some reason the timer wasn’t working. I’d like to tell you I fixed the board but I actually swapped in a spare one that I happen to have!

 

Anyway, now I can accurately save and restore programs!

 

Thanks.

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