Recent content by Bruce Tomlin

So it's picky about chips, but I've found a few 27C512 and even two 28C64 chips that it's happy with. The next thing is to get RS-232 working, because that would be the best way to get some code running on it without having to go through the burn / erase cycle all the time. And that's made worse...

I've finally gotten around to trying to make some of my accumulated stuff work. The thing I'm working on now is a bare board from an early 1990s telemarketing dialer. The software has a 1994 date in it, so this would be shortly after the Telephone Consumer Protection Act of 1991 (TCPA). It was...

Oof, I didn't realize these were files inside of disk images. The only way that works is to make some kind of packaging utility that builds a fresh image from individual files.

If you put them in a git repo, you could add a separate check-in that corrects the errors. Then you have the original, tagged as such, plus an easy-to-diff record of the changes. Of course this is a bit harder to do with printed manuals!

Do you have a functioning cassette tape drive? A good .wav rip would be a start.

I know it's fun to argue about what's the best way to do a hash, but the simple fact is, it's premature optimization. The hash doesn't matter if the rest of the assembler doesn't work, but the assembler will still work if it uses a simple linked list.

Even with modern monitors, syncing to both NTSC RGB (either analog or TTL) and VGA is rather uncommon. (syncing to NTSC component is much more common, but it didn't exist until the '90s) This is because the frequency gap is so wide between 15K and 31K that it's hard to make a CRT that can do...

Here's from my assembler test files, it may not be tricky, but it should be more or less complete. (basically my "tests" are a bunch of .asm files that get assembled and then the .hex output is compared with files from another directory)

This is what Svenska was talking about. They are "tokens", but they don't need to be in the same symbol table with labels. When you get the next token from the line, the "get word" or whatever gets a whole chunk of alphanumeric characters, or just a single character, and returns a type of...

A test suite could be as simple as a few .asm files and .hex files generated from them. You then manually run a script that runs the current version and compares that it produces the same .hex files. In some ways it can be a rather leaky test, but you're still testing something, so it makes sure...

As far as I know, the only known software for this is unit in the "Petebug" thread, along with some attempt to reverse engineer it... https://forum.vcfed.org/index.php?threads/stunning-motorola-68000-system-made-by-computer-system-associates-usa-circa-1984.57947/ The other thread has better...

I don't know why I never noticed that LD SP,0600 in the reset button NMI handler. I've certainly had years to get familiar with the contents of that ROM. Anyhow, it's pointless because unless something interrupts it, nothing will use the stack until it can be loaded again, either by rebooting to...

Basically the main point of an ICE is to have control of the hardware that contains the CPU. It lets you test the real hardware with a real CPU that you can control manually, sort of like a front panel but more complicated. These days modern CPUs have built-in debugging support because signal...

It's really personal preference, though I can't ever recall CP A being used for that purpose, only OR A and AND A.

Nope, you can only LD (DE),A / LD A,(DE). I still don't know why it wouldn't let you do that. It might not do division. This is why I prefer to just use my own assembler and copy the result over. Yep, it's looking like it might not support much in the way of math. In a modern assembler you...