Tape loading

A project log for MSX on RC2014

in which I attempt to make an MSX1 compatible computer using RC2014, keeping to standard RC2014 backplane and modules as far as possible.

shiela-dixonShiela Dixon 05/26/2023 at 09:410 Comments

My original stated goal was to build an MSX1 computer but that's a bit vague. ie I don't really know when I've achieved that goal. What didn't say but always had in mind is that I really wanted to be able to load and play one particular game from tape. 

My own nostalgia is for computers that had BASIC on startup and tape saving/loading, so I feel that the tape loading is an essential part of this project.

The reference circuit I used has an op-amp to turn an audio signal into a logic signal. Here's the circuit on a breadboard, in which I had very little confidence.

Imagine my astonishment when the game loaded on the first try....

(It's a new-ish game from futurewas8bit on a multiformat tape. Playing it here on my MSX2014 has checked off one more format, leaving just one of the eight to go.) 

t's a great game and this MSX version is a particularly good one. It's very addictive and my 'arrow key' hand ached after a while. This is the incentive I need to build the joystick circuit!

The thing that I'm finding harder than building the working tape and joystick modules is how to organise them and how to connect them.

Electrically it makes some sense to build the tape and joystick modules on one board.  But from a user point of view that makes no sense and gets away from the modular nature of this build, so I think they should be separate modules.

But that introduces some problems with connections. The tape interface (assuming we want both loading and saving, which we do) involves one connection to the sound module (because sound chips weirdly also tend to handle some of the i/o) and one connection to the PPI module.  The joystick module also needs connections the sound module. 

I've already used the spare lines on the bus for the very important slot selection lines.  I could use lines on the RC2014 enhanced bus, but I'd like this project to be buildable with the standard backplane. 

While I think about that, I'm going to play more Rodman.