Computers Overview
Commodore PET
Sinclair ZX80
Sinclair ZX81
BBC Micro
Sinclair Spectrum
Memotech MTX
      FDX Power
      FDX Systems
      MTX Capacitors
      MTX Power
      MTX RAM
      MTX VRAM
      Video Wall DDFS
    User Groups
    Video Wall
Memotech CP/M
Atari ST
Commodore Amiga
DEC 3000 AXP
Raspberry Pi



The Memotech MTX Series

Video Wall "Reflex"



The Video Wall "Reflex"

The April 1990 issue of Lighting & Sound International, available in the Library pages, describes the installation of a Memotech Video Wall as part of the sound & lighting upgrades to the Hammersmith Palais in 1990. The article briefly mentions the "Reflex Touch Controller", this device allowed the operator/DJ to "instantly access pre-programmed Video Wall sequences using a 32 button keypad". Other that this reference, I had been unable to find any other information about the Reflex unit until I obtained a collection of Video Wall hardware in 2013.

The photo at the top of the page shows one of the "black boxes" in my Video Wall bundle, this module has two Memotech labels on the base, one identifying the module as a "10 x 1 Reflex", the other marked "MTX2019R" - the same as the model / serial number printed on the rear of the case.

The rear of the Reflex unit showing the input/output connections.

The Reflex unit was initially faulty - the PSU had failed, making it necessary to open up the case, this revealed how the Reflex system was put together :-

As the photo shows, at its heart is an MTX computer board along with a board that I was previously unaware of - a combined RS232 and ROM board.

The majority of the standard MTX power regulation circuitry has been omitted from the computer board and instead, the DC voltages were provided by a Skynet model number SNP-3031 PSU, supplying +5V, +12V and -12V DC. The -5V DC required for the Video RAM is supplied from the -12V supply via the standard MTX Zener diode, ZD3. The main-board RAM has been upgraded to 256kbytes in the same manner as an MTX512S2 and the Video "daughter board" has not been installed. Modifications have been made to the video circuitry to enable a monochrome composite video signal to be taken directly from the TMS9929A video display processor.

It can be see that the connectors on the rear panel interface with the MTX and RS232 ports and we can deduce how the Reflex system must have operated. The Reflex has the key components that are installed in the MTX512S2 that is also part of my Video Wall equipment, i.e., a MTX computer with 256k of RAM and a ROM card containing the Video Wall software making up a diskless Video Wall system. The ROMs contained a copy of CP/M along with the Video Wall software, when the system was powered on, it booted CP/M, created a RAM disk using the memory in the MTX, copied the software from ROM to RAM and started the Video Wall program.

This Reflex supported a monochrome "prompt" monitor through the BNC "Video Out" connector, an external EBU/SMPTE Time Code input connected to the MTX "Ear" port through the "TC Input" 3.5mm jack socket and enabled control the Video Wall DDFS through the MTX Centronics port through the Reflex Centronics connector. The rear panel has a blank connector labelled "Keyboard" which could have been cabled to the MTX keyboard header if an external keyboard was required, but as this is not fitted, the Video Wall would have to have been controlled using a "remote". Andy Key recalls that there was small keypad used with some Video Wall systems. Unfortunately, my system is missing this separate keypad.

The Memotech Video Wall Product Description on the Manuals page describes how a Video Wall system could be controlled using commands over an RS232 serial link. With no keyboard connector fitted, this Reflex unit could only have been controlled via the RS232 connector - this is likely how a Reflex Touch Controller was interfaced to the Video Wall system.

As I was unable to repair the failed PSU and the SNP-3031 is obsolete, I spent a while trying to find a low cost replacement solution, perhaps using a PC "micro" PSU. I did not manage to find an alternative PSU that matched the voltage/current ratings of the SNP-3031 that could be fitted into the case without some difficulty, but I did find that the replacement Skynet product, the SNP-9031 is still available and at reasonable cost, so purchased a new one.

After installing the new PSU, checking the voltages and powering up the Reflex, I was confronted with this screen display on the prompt monitor.

Obviously, the unit still had a problem and needed further investigation to determine whether there was just a video display problem or whether there were more serious faults present.

I removed the ROM board Video Wall ROMs and tried to boot the MTX from its standard ROMs, this was unsuccessful, it resulted in a solid black display, although without the horizontal white lines. I tried various things, including installing the Reflex MTX computer board ROMs in another MTX, where they operated normally, as well as swapping out the CPU, CTC and VDP - again, with no improvement.

I was able to take a dump of the Video Wall ROMs that Andy was able to interpret and extract the start-up configuration and provide the following details :-

The first ROM is an 8KB RSCPM boot ROM followed by the first 56KB of initial RAM disk content and the second ROM is the next 64KB of that initial RAM disk content An RSCPM is the combination of an SCPM ROM (using 56 column VDP text) and RCPM ROM (copying ROM to RAM disc).

[Details of how the RSCPM boot ROMs work can be found on this page on Andy's site.]

After booting CP/M, the STARTUP command would execute "VS108R F8\F1", which would run the "VS108R" program an pass simulated keystrokes "F8" and "F1" to it.

The Video Wall Product Description helps us decode the meaning of the start up string :



VS Program name prefix, "VS" is unusual, it would normally be "VW"
10 Software Version, in this case, Version 10
8 Video Wall Size, in this case 8 x 8
R Control option, in this case, "Remote" control
Program Start-up String
F8 Special Options Menu
F1 Enter Remote Mode

The Video Wall software in the ROM would therefore appear to suggest that this Reflex was intended to control a very large Video Wall system, consisting of an 8 x 8 matrix of 64 screens.

The Cameron Video Wall User Manual contains information on the commands used by an earlier version (5.x) of the Video Wall software, it is believed that later software versions, including version 10.x installed in the Refelx ROM would not have made significant changes to the user commands.

When started interactively, the Video Wall software would initially display a Main Menu similar to that shown here, loaded from the ROM of my MTX512S2 Video Wall computer.

Entered manually or on the start-up command line, "F8" would invoke the "Special Options" selection of the Menu, subsequently, "F1" on the "Special Options" menu would put the Video Wall software into "remote" mode.

The Cameron manual states that "Remote" mode was not included in Version 5.x of the Video Wall software, but "remote" mode is described in the Video Wall Product Description. In remote mode , commands to control the Video Wall through the operator interface, e.g., MTX computer or Reflex controller, would be received on serial port "A".

To try to determine whether the Reflex was operating at any level, I reinstalled the Video Wall ROMs and connected a terminal emulator to the serial port and tried to enter commands to "take control" of the system and issue commands over the remote link. The Reflex did not respond to any enquiry or control sequences over the serial port, I took this to be a good indication that the software was not actually running. (When the Reflex was eventually working, I discovered that this conclusion was incorrect - without the DDFS(s) connected to the Reflex, the software reports a "NO SYNC" error, does not enter remote mode and waits for an operator to hit the "ESC" key.)

Since the software did not appear to be running with the Video Wall ROMs installed and the screen output from the normal MTX ROMs was a solid black display, the symptoms were suggestive of  typical MTX RAM problems, which often result in a pure black screen with a constant audible tone, although in this case, the system has no sound output capability (sound is normally passed through the Video board).

Fortunately, the RAM on 256k MTX computer boards is installed in sockets, and whilst I did not have any replacement RAMs that I could use for testing, I was able to remove all of the on-board RAM and install one of Andy Key's external MTX RAM cards.

With the Video Wall ROMs removed and the external RAM card connected, the MTX started up and displayed the usual MTX "Ready" prompt, although it was obviously in monochrome.

Connecting a standard MTX keyboard to the computer board connector, the system operated in normal MTX 40 column mode and I was able to enter BASIC, use PANEL etc., demonstrating that the main computer board was now working correctly using the external RAM board.

With the Video Wall ROMs re-installed, the system now started up in 56 column RSCPM mode, displayed the PROM bootstrap message, executed and passed the standard 64k memory test, but then hung.


The RAM card was only pinned to provide 64k of memory to the system, allowing it to pass the base 64k memory test, but resulting in failure when it tried to create the RAM disk for the Video Wall software.

After re-pinning the RAM card to provide 512k of memory, the system was able to configure the RAM disk and start up the Video Wall software.

As with my other Video Wall MTX512S2, the CP/M start-up screen is only displayed for the briefest of moment - making it difficult to capture., but displaying the messages shown in this poor quality image!

If you are very quick, you can hit <ctrl><c> between the Boot F51 message being displayed and the Video Wall software being loaded to interrupt the start-up sequence and gain access to the CP/M A> prompt.

This is of limited use, but you can see the Video Wall software program and sequence file names on the RAM disk..

The video display quickly switches to 40 column mode and displays the Video Wall Main Menu graphic - the screen layout confirming that this system was indeed intended to control a 8 x 8 screen Video Wall.

With no DDFS(s) connected, the "HIT (ESC)" prompt remains on the screen until the operator responds - if there is a keyboard present. With my test setup, I still had an MTX keyboard connected.

After hitting <ESC>, the normal Video Wall software menu is displayed.

The F8 key brings up the "Special Options" Menu, from where the Remote mode can be manually enabled.


If Remote mode is enabled, either manually, or automatically by the start-up command string, a message to that effect is displayed on the prompt monitor.

With the Reflex now functional, the final step will be to repopulate the on-board RAM sockets with replacement memory - as the internal photo shows, there is no room inside the Reflex module to allow the RAM board to be permanently installed.

Whilst I am pleased to have a functional Reflex unit, it is evident that I do not have the remainder of the hardware required to construct a 64 screen Video Wall - that would require 8 DDFS units and I have only one, confirming that I appear to have a selection of various items of Video Wall hardware, rather than a single Video Wall system.

Return to Video Wall Overview

mailto: Webmaster

 Terms & Conditions