Tag Archives: 6502

Zolatron 64 roundup

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This is the 300th blog post on this site, and I thought it would be appropriate to mark the occasion with a summary of what’s happening with my Zolatron 64 6502-based homebrew computer project. You see, the thing is, I’m feel like I’m about to announce ‘mission accomplished’ for this project. And that’s not something I get to say very… Read more »

Zolatron 64: 6502 bare metal random

There’s a problem when you build your own computer and therefore have to write your own operating system. All the things you rely on when coding in other environments – such as maths functions – are not there. You have to write them yourself. The Zolatron 64, like most homebrew computers, is effectively a bare metal project. I’m writing all… Read more »

Zolatron 64: being persistent

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In an earlier post, I described how I can now load software on to the Zolatron 64 6502 homebrew computer. The LOAD command was pretty basic – you couldn’t specify a file. Instead it just loaded the same file (zd.bin) which I’d have to overwrite if I wanted to load different code. Well, those days are over, and the Zolatron… Read more »

Zolatron 64: The start of an operating system

Let’s be clear about this, I have no idea how you write an operating system. I just know you need to have one. When I first started writing ROM code for the Zolatron 64 (Z64) 6502-based homebrew computer all that really mattered was getting things to work. And I was amazed when they did. I was following in the footsteps… Read more »

Zolatron 64: Creating a disk drive (sorta)

As I mentioned before, the Zolatron 64 6502-based homebrew computer (Z64) needs some kind of persistent storage. And these days there is no shortage of options. If you search around the interwebz for homebrew projects you’ll discover a treasure trove of clever solutions. But many of these involve implementing some form of existing technology. For example, you can employ a… Read more »

Zolatron 64: Interfacing the 6502 with the Raspberry Pi

Pretty much every computer needs persistent storage. And these days we’re spoiled for choice – everything from hard drives down to micro SD cards being capable of holding more information than I can comfortably imagine. With clever interfaces, these options are also open to builders of homebrew computers, like the 6502-based Zolatron 64 (Z64). But it does mean grappling with… Read more »

Zolatron 64: Using the 6522 VIA’s timers – part 1

There’s no getting away from it. The 6522 Versatile Interface Adapter (VIA) is, well, versatile. Alongside giving you two 8-bit general purpose I/O ports – much like the GPIO pins on a Raspberry Pi, Arduino and the like – it also has a bunch of handy extra features. These include a shift register and control lines that you can employ… Read more »

Zolatron 64 – more boards, bodging and blinkenlights

Well the Zolatron 64 homebrew 6502 computer is getting spiffed up in all sorts of ways. So here’s a quick catch-up before the next big challenge. Backplane The original backplane has been working fine. But I decided to upgrade it anyway. The connectors for the boards were a little further apart than they needed to be. And the new backplane… Read more »

Zolatron 64 ROM code – write, debug, repeat

With the basic hardware of the Zolatron 64 6502-based homebrew computer working fine, I’ve been spending most of my time on the ROM software. It turns out that writing an operating system in 6502 assembly code is harder than you might think. Well, anyway, it’s harder than I thought. But first… A quick catch-up on the state of play with… Read more »

Zolatron 64 – mein gott, it werkz!

Sorry about the headline. When I get excited, my German heritage sneaks out. But godammit, it’s justifed. Okay, so the first attempt at creating PCBs for the Zolatron 64 6502-based homebrew computer was not an unalloyed success. I never got as far as testing the backplane, serial board and VIA board because of a monumental screw-up on the main processor… Read more »

Zolatron 64 – first PCBs

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Well, how exciting. The first versions of the PCBs for the Zolatron 64 6502-based homebrew computer have arrived, and they are very pretty. Which is just as well… I say that because at least some of these boards will serve no purpose other than as decoration. I’d made some mistakes – one annoying, one stupid but survivable, and one idiotic… Read more »

Zolatron 64 6502 homebrew – moving up to real hardware

You can only go so far with a breadboard. Those things are great for quick and dirty prototypes and experimentation. But there comes a point when a breadboard is an unhealthy basis for a project. And yes, I’m aware that many people have followed Ben Eater‘s lead in building 8-bit processors and 6502-based computers on breadboards. I include myself among… Read more »

Zolatron 64 6502 homebrew – processing commands

In an earlier post, I described how I was parsing commands input (via serial) into the Zolatron 64 8-bit homebrew computer in assembly language. That parsing process matched an input command with an internal list and the result was a ‘token’, a single integer value of $80 or more representing that command that is placed in a memory location. Or… Read more »

Zolatron 64 6502 homebrew – converting between text and numbers in assembly

One thing it was obvious I would want to do with the Zolatron 64 6502 homebrew computer is have a routine to display the contents of sections of memory – à la Wozmon. There’s a snag, though. The content of any given byte in memory is a number, in the range 0-255. But to display this on the screen, this… Read more »

Zolatron 64 6502 homebrew – better LCD printing

A quick recap. The Zolatron 64 6502 homebrew machine is at the point where it can print messages to an LCD screen and send and receive messages via the serial port. Most of the time. The incoming messages are put in a buffer and then printed to the LCD. And a fat lot of use that is. I wanted to… Read more »