Description

Hardware

The Canon Interface Unit DMB is a device conceived for the Canon T90 Single-lens reflex (SLR) camera and released in 1986.

First, you need to add the Canon DMB-90 module to the camera. This module has a LCD panel displaying the parameters and several buttons to change the settings. DMB-90 means Data Memory Back 90.

Then, you can connect the camera to a MSX computer by using the dedicated interface. The connection is made with a 6-pin connector attached to the interface. It was recommended to use the following Canon computers:

Canon V-10
Canon V-20 and its localised versions: V-20 (EU), V-20 (FR)
Canon V-25
Canon V-30F

However, it can actually be used on any MSX computer with at least 16kB RAM without any problem. The MSX computer does not need an internal or external RS-232C interface, so it seems that the Canon Interface Unit DMB has such interface built-in.

The interface has a 2kB RAM to store data for 156 frames (4 rolls of 36-exposure film) or 338 frames (9 rolls of 36-exposure films), according the number of parameters used:

in the standard mode, 13 parameters are stored: shutter speed, aperture value, metering mode, shooting mode, use flash or not, aperture stopped-down or not, use exposure compensation or not, number of exposures made, ISO film speed, use manual exposure or not, frame number (a 4-digit up-counter coupled to exposure), auto calendar (Year/month/day, hour/minute), manually set lens data (8 program settings)

in the reduced capacity mode, only 6 parameters are stored: shutter speed, aperture value, aperture stopped-down or not, number of exposures made, use manual exposure or not, frame number (a 4-digit up-counter coupled to exposure)

The module was sold as DMB-90, the interface as Interface Unit DMB. They were not available in North America and some other areas.

Firmware

The interface includes a ROM that displays a specific menu on the MSX computer with 6 options:

DUMP: transmit the data stored in the DMB-90 RAM to the computer
SET IMPRINT (a 6-digit number to be imprinted on the film) or SET LENS (four kinds of lens data)
DISP: display the data for 6 frames on the MSX screen
CSAVE: save data stored in the MSX memory on tape cassette
CLOAD: load data from tape cassette to the MSX memory
END: quit the menu

A SEARCH feature is included in this firmware.

Software

Additional software was provided on a cassette for inserting comments and for the TIMER and IMPRINT functions, it can display on the MSX screen 3 extra parameters (spot metering data, FE locking data, amount of exposure compensation). It is possible to print all the data by connecting a printer to the MSX computer.