History and Overview

Even though my focus layed on the Commodore C64 site I was always addicted to 6809 based systems (for ease of programming). Affordable systems these times were Dragons or CoCos. In 1987 I finally got one, a Dragon 32 which I had expanded to 64 Kbyte later on. No other devices, especially disk drive and so on found the way to me. So in need of some practicable mass storage - the tape drive wasn't a solution to this - I thought of to use my good old Commodore 1541 floppy drive. The (alas slow) serial IEC tranfer protocol was not the problem. Some shortcut Basic commands has been added to extend the Color Basic with all the operations needed: show the directory, save and load programs, check error messages, submit special floppy commands, redirect output to some other IEC device (e.g an IEC printer, I had a Commodore MPS-801 matrix printer).

I started the project in 1987 and got it to work soon. I decided to use a separate interface plugged to the expansion port with a 6821 PIO. Altough the parallel printer port could be used for this, I planned to support parallel transfers too (my drive is SpeedDOS+ extended). But this was'nt realized so far. :( Another aspect is that I was afraid to harm my Dragon and therefore I thougt a separate circuit (extra PIA) would protect the Dragon. In case of an electrically failure probably only the PIA has to be replaced.
The interface is a quick and dirty hack of hardware stuff (really not intented for serial production).

Author: Johann E. Klasek
Copyright notice: These documents may be copied and redistributed as long authorship and source is mentioned.

Sources & Binaries

From 1987, 1991, reworked and extended to 2016...

1. Listing of driver version 32, 2016 edition (IEC32 advanced) (bugfixes, optimized, small extensions)
   Uncomment line ;systype set syscoco to assemble a CoCo binary.
   • Assembler list output
   • Binary (for Dragon 32, in PRG format, skip first 2 bytes used as loading address)
2. Commented Listing of driver version 32 (IEC32) (based on original code)
   Uncomment line ;systype set syscoco to assemble a CoCo binary.
   • Assembler list output (producing iec32.orig.prg)
   • Assembler listing disassembled from binary (with 6809dasm from iec32.orig.prg)
   • Binary (in PRG format, skip first 2 bytes used as loading address)
   • Binary as .WAV file
     To load and start with
     CLOADM
     EXEC
     Beware: It won't work with an emulator, Xroar e.g. simply hangs, because the mapping for the 6821 IC is missing and no stable read of the input port is possible.
     See small command reference.

Original Project Documentation

Some scanned documents, binaries and data from 1987 and 1991 ...

1. Listing of driver version 32 (IEC32) (PDF, scanned printout, 1991-03-13)
2. Driver software description (PDF, handwritten, german, 1987-02-22)
3. Circuit schema of the interface (PDF, 1987-02-22)
4. Dragon 32 Expansion Port (PDF, handwritten/sketched)

Prototype

The front picture was taken without the PIA 6821 (empty DIL 40p socket).

Front	Back

Basic extension command reference

1. prgcat.pl: Perlscript to decode Color Basic binaries (untokenize, expand)
2. token.pl: Module for prgcat.pl (included)

Future Plans

What currently comes to mind ...

• Improve the documentation: clean schematics, english descriptions and documentation.
  Partially done: Source code provided.
• Support of the Dragon 32 parallel printer port (instead of the separate interface card).
• SpeedDOS+ Interface support (parallel transfer mode)
• Burst-Mode transfer mode
• Emulator integration (e.g. Xroar with OpenCBM on VC1541 connected to a PC) ...

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