Has anyone ever come across a 'Microcolour' terminal? It was made in the
UK by Microvitec, who were better known for monitors (often BBC micros
were used iwth Microvitec Cub monitors).
I have a couple of the Microcolour base units here, no monitors or
keyboards. Here's what I've discovered so far...
On the rear are connectors for 'Host' (DB25 plug), 'Printer 1' (DB25
socket), 'Printer 2' (DB25 socket), Monitor (DB25 plug), Keyboard (DE9
socket), mains in/out (mormal IEC connectors, a couple of fuses and the
on/off switch. The only feature on the front is a green power-on LED.
Insdie is a PSU (the 2 units I have differ in the PSU design, but that's
not vert important at the momnet0 nd a crdcage containg 3 PCBs (with
aslot for a 4th). These plug into a backplane at the front fo the machine
using 64 pin A+B DIN41612 connectors.
The loweremost PCB carries the Host, Printer 1 and Keyboard connectors.
On this board are the processor (6809), EPROMs, RAM (some of which is
battery-backed -- I have removed the leaking NiCdsm there is no other
damage), 4 6551 serial chips (for the printer 1 port, which is RS232 DTE,
even though it's on a socket :-(), the keyboard port (TTL level), and the
host port (it uses 2 6551s for this so yuo can have split baud rates I
guess), a 6821 (used at least for the Printer 2 port which is thus a
parallel interface, a cable rund from a SIL header on the PCB to the DB25
socket o nthe chassis), etc. One of the EPROMs has a label 'Regis' which
seems to suggest what protocol it may use.
The other 2 boards are video-relates. One seems to be text video (6845,
several 6116 RAMs in a row on one edge, another couple of 6116s which may
well be programmable character generator, there's no EPROM on this
board), and lots of TTL. There's a 10 pin header which is linked ot part of
the monitor connector.
The last PCB seems to be graphics related. It contains 128K of DRAM, some
74S189 SRAMs for a oolour palette and again lots of TTL. There's a 15 pin
header that links to the montior conecetor.
Now for the monitor connector. It's a DB25 plug. One pin is not fitted,
one is wired to chassis ground. 9 of the remainder go to the text PCB
(one pin on the header is not used), the remaining 14 go to the graphics
board (again one pin on the header is not used).
Now fo the odd thing. All those signals are TTL level. The output of the
graphics board (12 pins on the header) are the outputs of those palette
RAMs. In other words 12 bits digital (I asusme 4 bits each for R,G,B).
The otuput fo the text board is similarly a 4 bit value (I think). And of
course there are 2 sync signals, which I could identify.
Vsync is 50Hz (not too suprising), HSync is 21.8kHz. In other words, EGA
rates .Sothis thing used a specail EGA-like monitor with many more input
bits. I suspect I am goign to start by hooking up a normal EGA monitor
(assuming I can find one, I think I have a 5154 around here) to see if I
can get some output, albiet with fewer colours than I should have and
then try modifying such a montiro t oincrease the numebr of bits on the DACs.
As for the keyhoard, at least it's synchronous serial (of the pins on the
DE9, there's TTL level TxD and RxD, ground, +5V, +12V, -12V). I have no
idea of the baud rate, etc, but if necesary I cna use a logic analyser to
see how it initialises the appropriate 6551.
-tony
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Likely it is a viewdata terminal, lots were used at the stock exchange
and also in travel agents.
Dave Caroline
Likely it is a viewdata terminal, lots were used at the stock exchange
and also in travel agents.
I'm darn sure it;s a lot more than that...
You do not need 128K of graphics RAM and a palette for viewdata.
And it's a fair bet that the 'Regis' on the ROM label means it uses that
DEC protocol.
-tony