PDP-8e Monitor Program with TD8-E Support

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Martin Eberhard

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Apr 13, 2020, 7:44:23 PM4/13/20
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Stuck "sheltering in place" at home, I've just completed testing of version 1.00 of my "MEMON-8" monitor program for the PDP-8e, with a TD8-E subsystem. Using a simple command-line interface, this program allow you to:

* Examine, change, copy, verify, and execute core memory
* Read, write, and verify blocks from DECtape
* Send, receive, and verify entire PDP-8 ".TU56" files, writing them to, or creating them from DECtape.

The .TU56 routines transfer data to and from the PDP-8 using the Xmodem protocol, which does flow control, as well as error checking. While this method is less byte-efficient than other .TU56 file loaders, it has the advantage of not requiring a special program on the PC-side. MEMON-8 works nicely with programs like Tera Term or Hyperterm.

I've modified one of my KL8-E boards to run at 38.4K baud. At this rate, the serial port transfer time is about the same as writing to or reading from DECtape - it's pretty balanced, and the overhead from the inefficient byte packing is not so bad.

I am especially pleased with the XV command, which allowed me to compare an entire DECtape from my collection with the equivalent .TU56 file available online, to see if they were in fact the same version, and whether or not my tape was corrupted.

If you are debugging a PDP-8e with a TD8-E subsystem, you'll find this program handy. Even without a TD8-E, it's a pretty nice monitor for poking around the PDP-8's memory.

your feedback is very welcome!

Download the program and the Users Manual here:

https://tinyurl.com/uvg2lwq

or here, (if you prefer the "real" URL)

https://deramp.com/downloads/mfe_archive/005-Documentation%20and%20Code%20by%20Martin/010%20Code%20by%20Martin/DEC%20PDP8%20Code/MEMON-8/

Best,
Martin E.

vher...@me.com

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Apr 14, 2020, 5:02:50 PM4/14/20
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Hello Martin,

this is a fine work you did! I was able to do most things that are in your documentation. With the second serial interfacel at 40/41 I was able to send characters (PT). I use minicom with 115200 on linux side, with my modified M8650 that works well with os8diskserver. While receiving the tape in minicom I try sending wit XS, but the tape loops , I think at block 0. A second tape the same, but there is no problem with the tape. It boots and works without conspicuity.
Do you have an idea what I'm doing wrong?

A second thing, when relocating the program to other fields, the CO (CO 20 50020 4200) went OK, But after EX 50200 the pdp hangs. I have to start at the new position by the frontpanel. I tried a few times, always the same.

Best regards
Volker

Martin Eberhard

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Apr 14, 2020, 5:24:04 PM4/14/20
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Hi Volker,

Can you tell me what revision it says on the sign-on banner? I had very briefly uploaded the wrong version, and I think you might have downloaded that version before I caught my stupidity. Is it 1.00 or 0.08? If it is not 1.00, please go get the correct version! (same place.)

Thanks,
Martin E.

Martin Eberhard

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Apr 14, 2020, 6:06:30 PM4/14/20
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>A second thing, when relocating the program to other fields, the CO (CO 20 50020 4200) went OK, But after EX 50200 the pdp hangs. I have to start at the new position by the frontpanel. I tried a few times, always the same.

I bet you a nickel i know why this one doesn't work (because I just did the same thing myself...) I bet you actually typed "EX 50020" not "EX 50200". Try it again, let me know :-)

Martin Eberhard

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Apr 14, 2020, 6:36:58 PM4/14/20
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> this is a fine work you did! I was able to do most things that are in your documentation. With the second serial interfacel at 40/41 I was able to send characters (PT). I use minicom with 115200 on linux side, with my modified M8650 that works well with os8diskserver. While receiving the tape in minicom I try sending wit XS, but the tape loops , I think at block 0. A second tape the same, but there is no problem with the tape. It boots and works without conspicuity.
> Do you have an idea what I'm doing wrong?


Hi Volker,

You are doing nothing wrong! I screwed up when I release version 1.00, failing to save after I had fixed this bug. I now present Memon-8 version 1.01, which has this bug fixed.

Thanks you for trying it so quickly!

Same place: https://tinyurl.com/uvg2lwq

Martin E.


Martin Eberhard

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Apr 19, 2020, 3:17:13 PM4/19/20
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I've just posted MEMON-8 version 1.04 in the same place for the new code and the new user's manual:

https://tinyurl.com/uvg2lwq

This version fixes a bug in my Xmodem retry algorithm, plus incorporates several improvements. (Thanks to Volker for the testing and great suggestions.)
Improvements:

1. It works now when the transfer port is set to be the same as the console port, though obviously with reduced error messages

2. A new TB command allow you to boot from tape

3. The tape is rewound at the end of the tape image transfer commands

4. The User's manual includes these improvements, as well as more verbose discussions for some of the other commands.

best,
Martin E.

Christian Corti

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Apr 20, 2020, 4:20:03 AM4/20/20
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Martin Eberhard <mfebe...@gmail.com> wrote:
> I've just posted MEMON-8 version 1.04 in the same place for the new code and the new user's manual:

And now for a TC08 version for those of us who have real controllers ;-)

Christian

Martin Eberhard

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Apr 29, 2020, 7:25:11 PM4/29/20
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I've just posted Memon-8 Version 1.08.

The significant improvement in 1.08 is the addition of two commands to read tape blocks while the tape is moving in reverse.

I have found while recovering old tapes with marginal data that sometimes a block with read errors when the tape is moving forward will read successfully when read in reverse. I've made a few other small tweaks to the program along the way.

-Martin E.

Martin Eberhard

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Apr 29, 2020, 7:26:05 PM4/29/20
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...same place:

https://tinyurl.com/uvg2lwq

Martin Eberhard

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Apr 29, 2020, 7:28:20 PM4/29/20
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> And now for a TC08 version for those of us who have real controllers ;-)
>
> Christian

(-: you are just making me envious, Christian. If I had a TC08, I would love to write that version!

But my source code is freely available, so if you get enthusiastic, start with my code.

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