Mera Elzab 7951 OM
This device was probably designed to be compact,
simple and cheap, as it uses only 74 logic and no (V)LSI circuits. It
was used in Polish Railways to communicate points of sale with computer
systems. Its features aren't high-end: 40 characters in a line and 12
lines could be displayed, the only port is one serial port, keyboard is
not much comfortable, and case is made of quite thin plastic covered in
white paint. Speaker was built-in and made a sound each time key was
pressed. Fortunately, there was a volume trimmer.
There were also some versions with amber CRT, but my unit is the most popular device with green one.
|Memory:||1KWord (6-bit word) display memory|
|Keyboard:||Internal, parallel connection|
|Main port:||Serial port?
Peripherals in collection:
Unfortunately my unit doesn't work, it displays garbage on screen and even doesn't blink cursor. Timing seems to work as picture is generated and display memory is thrown, display memory itself is also good, but something must be wrong with TTL logic chips... yes, 90% of mainboard.
7951OM is a very basic device, which has a logic to generate cursor,
feed character generator with characters from port and feed port with
characters from keyboard. Display generator uses 2716 EPROM, but it's
made pin-compatible to MCY7304NAB ROM. It uses six 1Kbit memory chips to
store screen contents (64-character table, uppercase only), but half is
used, as it has 40x12 character mode.
Power supply unit is prone to overheating, there are 2 transformers in a steel cover.