Author Topic: Investigating the TRS-80 ROM - 1981 style  (Read 918 times)

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Offline DrG

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Investigating the TRS-80 ROM - 1981 style
« on: July 14, 2021, 04:46:59 pm »
Back in the day, it was a big deal (at least for me) to explore the TRS-80 operating system in ROM. No open source there, but many painstakingly disassembled the code and published the results (not always completely accurately). Here is one example.





With today's standards, it's a little difficult to explain to younger folks, but it was truly exciting and fun. Plus, it was a great way to learn Z80 assembly beyond the few books...."Ohhhh that's what their doing there" :) and then you would use it in your own code and you could do all kinds of cool stuff.

I know such challenges still exist, but somehow they do not seem as much fun.
« Last Edit: July 15, 2021, 01:04:11 am by DrG »
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Offline DrG

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Re: Investigateing the TRS-80 ROM - 1981 style
« Reply #1 on: July 14, 2021, 06:22:42 pm »
...and yes, in case you noticed, those are not complete opcode mnemonics and it was intentional.



Made it more fun and disassemblers were plentiful (and also did not always work right :) ).
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Offline SiliconWizard

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Re: Investigateing the TRS-80 ROM - 1981 style
« Reply #2 on: July 14, 2021, 06:58:56 pm »
...and yes, in case you noticed, those are not complete opcode mnemonics and it was intentional.

I did.



I see the reasoning. Reverse-engineering is OK, but publishing the exact code would be infringing copyright. I'm not completely sure that would be true, though. I remember publishing source code was discussed in other threads, and unless you copied the exact original source code (which it wouldn't be here in any case, even if it was a complete disassembly), then you wouldn't infringe the copyright per se. IMHO. This is probably on the edge, though, and the authors of the book were likely not willing to bother risking to be sued by MS.

Of course, *using* the code in a product without MS consent would be infringing, but merely publishing non-original source code for the purpose of reading it? Not completely sure. Just a thought. That's probably legal subtleties here.
 

Offline Phil_G

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Re: Investigateing the TRS-80 ROM - 1981 style
« Reply #3 on: July 15, 2021, 12:50:37 am »
I still refer to this quite frequently - "More TRS80 Assembly Language Programming" by Bill Barden from 1982.
Doesnt have a full ROM disassembly but its full of interface code and ideas

« Last Edit: July 15, 2021, 12:52:46 am by Phil_G »
 

Offline DrG

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Re: Investigating the TRS-80 ROM - 1981 style
« Reply #4 on: July 15, 2021, 01:09:46 am »
Yeah, I remember that one - it's a little later (MIII on the cover) and I think Bill Barden wrote an earlier one that I might have.

There were also the "Mysteries of" series and I know I have or had the one on Disk OS, which I see on Amazon for several hundred bucks (not saying anyone bought them for that price). https://www.amazon.com/Trs-80-Disk-Other-Mysteries-Pennington/dp/0936200006

I need to go look through some boxes tomorrow :)
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Offline Phil_G

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Re: Investigating the TRS-80 ROM - 1981 style
« Reply #5 on: July 15, 2021, 12:49:29 pm »
Thats right, Bill did a previous TRS80 assembly book but I've never managed to find one.  My Nascom replacement was an Eaca Genie, which had much in common with the TRS80, hence buying the book - nothing Eaca-specific was available :-)
I've a box of 40-year-old Genie and Nascom cassettes so recently I've been experimenting with a stand-alone tape reader which was partly successful - most of the tapes are bad with layer bleed-through.  Should have spun them occasionally!
 

Offline DrG

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Re: Investigating the TRS-80 ROM - 1981 style
« Reply #6 on: July 15, 2021, 04:09:41 pm »
Thats right, Bill did a previous TRS80 assembly book but I've never managed to find one.  My Nascom replacement was an Eaca Genie, which had much in common with the TRS80, hence buying the book - nothing Eaca-specific was available :-)
I've a box of 40-year-old Genie and Nascom cassettes so recently I've been experimenting with a stand-alone tape reader which was partly successful - most of the tapes are bad with layer bleed-through.  Should have spun them occasionally!

So, I did go look in some boxes and I am glad I did because I found both of the Barden books (and several other gems)!



I did not immediately recognize the machine you referred to and looked them up https://www.classic-computers.org.nz/system-80/hardware_eaca-genie-III.htm I do faintly remember the Genie machines. The Genie III was quite sophisticated for the time (1982), CP/M capable and with TRS-80 M1 compatibility and running NewDos. If you still have it, post a pic or two please (unless you already did and I missed it).

RE: your cassette tapes. Did they use the TRS-80 format? You may want to check out https://www.eevblog.com/forum/vintage-computing/trs-80-data-dubber-(cassette-fixer)/ It could be helpful.

Edited to add:

Also found the 1977 Zilog manual. Leafing through it today I remember it being very difficult to understand at first. All I really had for reference was some experience with a KIM-1 (6502). It reminded me of how much easier Barden's book made, for lightweights or not, I was appreciative.


« Last Edit: July 15, 2021, 08:23:02 pm by DrG »
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Offline DrG

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Re: Investigating the TRS-80 ROM - 1981 style
« Reply #7 on: July 15, 2021, 04:11:54 pm »
...and here is Vol 1,  WooHoo!

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