Fawn Box

Mus.Cat. NEWUC:2015.28 Mnfctr: MARI Ltd Date: 1984 Ser. No: 0228 Model: -
Comp: Microcomputer Depth: 230mm Width: 220mm Height: 78mm Weight: 2Kg



Before 1992 the UK academic network JANET used X25 packet switching.
There were several protocols defining how to communicate over the network called the coloured
book protocols each identified by the colour of the cover of the specification document.

To explain the fawn box we have to explain something else - SSMP.
(The colour of the SSMP specification document was fawn.)
Simple Screen Management Protocol was a way of communication between a terminal
and a host machine. The user on the terminal would logon to the host machine to access their files
and applications on the host. If the terminal was an emulator on a microcomputer
eg BBC Micro, IBM PC, AMSTRAD 1512, or RM Nimbus that had SSMP support installed
the user could envoke a full screen editor of a text file. The display would be a
portion of the file about 20 lines, each line about 100 characters.

There was no mouse but cursor keys could move the cursor to somewhere in the text.
There you could delete or insert text. There was also CTRL-x commands to do global moves.
There was also a command to search for a piece of "text". And lots of other commands.

But in essence it was a WYSIWYG editor.What You See Is What You Get.

At last we come to the fawn box.

There was a lot of dumb terminals around, just a keyboard and screen.
Such as a DEC VT100, Hazeltine 1500,Televideo 9220, ...
The fawn box provided the processor power and firmware to enable the dumb terminal to use SSMP.

Unfortunately the price of personal computers dropped so fast that dumb terminals became old hat.


This is the front.

A 1 amp fuse socket and power ON/OFF switch.
SETUP and RESET buttons.


This is the rear of the Fawn Box.

Three 25 pin D connectors.
The first is CHANNEL C female socket so it was output from the Fawn Box to the host computer.
Then CHANNEL B and CHANNEL A male 25 pin D connectors.

I do not know but summise that this Fawn Box could support two dumb terminals
one connected to A the other to B the host to C.

The SETUP button would display a menu on the dumb terminal
where things like terminal type, speed, etc could be selected.

This is the motherboard in the box.

The largest 40 pin chip labelled D780-C is a Zilog Z80 4MHz 8bit CPU
it was INTEL 8080 compatible but much better.

Above it is a 28 pin chip with a circular window labelled D2764D,
This is an 8K x 8bit EPROM, (Eraseable Programmable Read Only Memory)
that held the SSMP firmware.

Above that is a 24pin empty slot and above that a 24 pin chip labelled CDM6116AE2
that is 2KB static RAM.

To the right of that is one of three 28pin chips labelled D8251AFC,
these are Universal Synchronous/Asynchronous Receiver/Transmitter (USART) chips.
These can read 8 bits in parallel from the RAM and transmit them serially to the channel,
and receive 8 bits serially from the channel and write them in parallel to the RAM.

Below the three USART chips is a 24 pins chip labelled D8253C-5.
This is 3 independant programmable 16 bit timers.


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