1 - Introduction

Reflex is a free package (previously commercial) which provides a complete emulation of a 6809 processor based computer system, running the TSC FLEX operating system over the Percom PSYMON monitor ROM with a useful command extension set. It runs under Win95; an older version is also available to run under the Amiga's OS (2.04 or higher). On a modern PC (By "modern", I mean anything later than a 60 MHz Pentium) the emulator is faster than the original computer system was.

ReFlex running under Windows XP

The 6809 is a 64k memory capable microprocessor with a decent register set and a very strong instruction set for an 8-bit CPU of its day. Motorola was the source of the design of the 6809; it was derived, somewhat loosely, from the 6800. It offered 6800 source code compatibility for the most part. The next step beyond the 6809 was the 68000 series.

FLEX is a small (Approximately 6k!) DOS which, along with CP/M and a few others, truly pioneered small personal computers. These were the systems that were already well in place when Apple Computer started in a garage. We're all tired of hearing about how Apple "started" the computer revolution. They didn't. They weren't even around at the time. Intel & MITS (the Altair 8800) started it. Period.

PSYMON is a low level system monitor that nominally is 1k. In this emulator, there is an additional 1k ROM extension I wrote which provides some additional capabilities to the monitor.

When I call the emulation "complete", I mean that I've provided...

  • A very comprehensive emulation of the original computer system.
  • All the commands and utilities you'd need to do real work.
  • Solid emulation.
  • Usable speed.

If you ran FLEX in the past, you'll likely experience a strong sense of nostalgia within seconds after starting the software. Welcome to the club!

This software provides emulation of all 6809 official* instructions with the exception of CWAI & SYNC. The virtual computer which the emulator creates has 64k of memory, 2k of which is ROM, or read-only. There is also a low-level "monitor"; this is called PSYMON. It originally came from Percom corporation.

*There are some undocumented instructions that work, or partially work, within some versions of the 6809 chips. These are not supported in the emulator; Motorola, the architects of the 6809, never supported or admitted to these various operations. Software that depends on these features will not function as intended. Also, Hitachi created a chip called the "6309" which had some additional functionality. That functionality is not emulated.

The software provides character I/O via emulation of a Motorola 6850 ACIA chip located at addresses $E008 and $E009, and aliased at $E004 & $E005. It provides Disk I/O via emulation of a powerful DMA disk controller that lets the Host do 99% of the work using the Host processor directly, which means that disk I/O is considerably faster under the emulation than it was for any conceivable 6809 system.

Unfortunately, this is pretty well hidden by the enormous amount of work that the emulation itself must do unless you have a reasonably modern processor (Pentium @ 60 MHz or better). Printer support is likewise handled by the Host processor directly as a DMA operation. Under FLEX, you just use the "P" command as you usually would. There is a menu that allows selection of LPT1: through LPT4: as the output printer.

Keyboard Navigation
, Previous Page . Next Page t TOC i Index g Glossary

Valid HTML 4.01 Loose

This manual was generated with wtfm
wtfm uses aa_macro and SqLite
aa_macro uses python 2.7
Please consider supporting my Reflex efforts via a small PayPal donation.