Anyways, I was wondering if anyone can help me understand the Videx card. I do have the ROMs, including font data, also the user manual going relatively in-depth for testing this card with a few lines of code; but I do miss altogether the knowledge on what the ROM firmware really does. Disassembling the whole thing is probably not enough to understand the intent behind every line of code. Once I can get this virtual peripheral to work, the good news is there's a lot of software I can test it with. The Videx interface standard was probably the most cloned among all Apple II cards at the time. I'm also curious to discover how it's so-called 'serial communication compatibility' meant in reality. Was it supposed to work in tandem with other cards ?I'm curious to hear some reactions. So here it is—enjoy!
That's a sad loss. At least my dad called me to come get whatever I still wanted from his place before he put shoveled out his garage into a dumpster. Fortunately I had already gotten my II+ gear before then.
You don't have to disassemble the firmware.
The source coude listing is in the manual starting page 5-15
https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Interface%20Cards/80%20Column%20Cards/Videx%20Videoterm/Manuals/Videx%20Videoterm%20-%20Installation%20and%20Operation%20Manual.pdf
Thanks mate. You may be right, I guess I'm trapped in a feeling of insecurity emulating a peripheral I am not able to test anymore in real life. I am practically reverse engineering a computer system quite literally from childhood memory.In some cases, I will unfortunately still need to check with some folks owning the real dinosour hardware. FYI, I've been reading Don Lancaster's old article yesterday about the vaporlock technique. It's obviously a hack , a well educated (but working) guess on vertical blank synchronisation, that I find very cool, but I think quite finnicky to emulate. Maybe it's only a fear again, but I think this is the kind of things that need experimentation on real hardware, since this specific algorithm is everything but deterministic, highly probabilistic indeed. Same for the mockingboard, I found some ROMs, even multiple versions of it, I know a lot about this device, but only God knows how this chipset is connected to the bus and how it generates waveforms, random noise and what not...
Well, that's been documented also:
https://www.wiki.reactivemicro.com/File:Mockingboard_Schematic_Arnold.pdf
and
https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Interface%20Cards/Audio/Sweet%20Microsystems%20Mockingboard/Schematics/
As I wrote a Javascript based emulator for an ApppleII+, I'm afraid I will have to dig deeper. I will have to aim at a model A, B or C. The Mockingboard D was tailored to the Apple IIc, and I learned by now it's the only one featuring a ROM chip... One worry less for me! Anyways, I already started coding the VIA chip emulator which acts as a gateway and interrupt timer per Yamaha synth chip, which in itself I also successfully emulated in a test project, but putting these two together... oh man!