How to build your own micro UK101!
by Grant Searle
Last update: 31st March 2008
Please note that you are NOT allowed to reproduce any of this page elsewhere on the Web without my permission!
Introduction
Construction
Parts List
Wiring diagrams
Circuit Diagram
ROM images
Pictures of the finished UK101
Using the micro UK101
Picture of the original UK101
Links to some of my other pages
For many years now I have been working with the latest technology using high-powered computers. However, nothing nowadays can replace the time when the first home microcomputers hit the streets. I am a keen collector of the home computer era. Follow this link to see my current collection. In those days you HAD to make your programs fit the hardware and memory available.
The micro UK101 described here is effectively the
"core" of the original UK101. I have removed the
display and the keyboard circuitry and, instead, used a terminal
emulation program (eg HyperTerm for Windows) as the
keyboard/display. This has resulted in a very simple circuit
which is suitable for use embedded-control applications as well
as a fully-functioning computer. I have tried to make as few
functional changes as possible to allow old software to work,
wherever possible. As a result the BASIC ROM is totally
untouched. Some patches have been applied to the CEGMON ROM to
ensure ALL I/O is via the serial port only, not to the screen.
The differences are illustrated in the table below:
| Original UK101 | The MicroUK101 |
| 3K RAM, expandable on-board to 8K | 32K RAM |
| 300 baud serial/cassette interface | 19200 baud serial interface. No cassette port needed as the PC can store the prorgams. |
| 16x32 display | All display via the terminal on the PC |
| TV output and serial I/O | Only serial I/O |
| 1MHz 6502 CPU | 1MHz to 8MHz CPU clock speed available |
| Keyboard input (32 keys soldered directly onto the board) | Input via serial connection |
| 12 inch x 15 inch board | 3 inch x 3 inch board |
| 1.5A supply current | 200mA supply current, probably less if CMOS CPU used. |
| Open-board construction (uncased) | Up to you! |
| Microsoft BASIC | Microsoft BASIC |
| Various monitors were available; CEGMON being a popular choice | CEGMON monitor. Patched to ensure all I/O is via the serial port only. |
This is an ideal project for anyone wanting to build their
first computer as there aren't many components and it can be
built using wire-wrap or on a breadboard (as I originally did
with this circuit) in a couple of evenings.
You will, however, need to blow your own EPROM image. A logic
probe or an oscilloscope will probably be a distinct advantage in
case it doesn't work.
Construction could be done in many ways, including the
following:
Assuming you are going to follow my layout, please see the wiring diagrams section for full details of
the component layout and the point-to-point wiring needed.
My version was built on a 3 inch square piece of tri-pad
Veroboard (ie. the copper tracks on the reverse have breaks
regularly resulting in groups of three holes being connected
together. See the reverse view for further
details). I used wire-wrap wire which requires soldering but,
instead of wire wrapping, I used it for point-to-point wiring
instead. All components are soldered in first then the wire laid
across the soldered joint and heated with the soldering iron
until the insulation melts completing the joint. Using this wire
for point-to-point wiring is very quick and the whole board was
soldered-up this way in a few hours.
Begin construction by positioning the IC sockets (see my pictures below for guidance). Next I recommend wiring the data and address. As each wire is soldered it, mark it off on the wiring diagram. This helps avoid any errors resulting from missing connections.
Wire the glue-logic wiring next, again marking each connection on the wiring diagram as you proceed.
Finally, wire up the power supply connections to all of the chips. For clarity, these are not shown on the wiring diagrams.
Once all components are soldered and without any ICs inserted
into the sockets, connect a continuity tester between the power
supply pins. If a short exists then check the underside of the
board for any solder bridges. If all is well connect a power
supply (current regulated to 500mA if possible). Check the +5V
and 0V connections on each IC socket. Turn off the supply and
insert the ICs. Turn on the power supply. If the circuit is
working then expect a power consumption of around 210mA. Connect
to a computer running a terminal emulation program set at 19200
baud, 8 bit, no parity, 1 stop bit, no handshake. Press the Reset
button. If you see the microUK101 prompt then well done!
This is a full list of discrete components required to build the UK101 excluding any hardware such as power supplies, nuts and bolts etc.
Component Type Qty No IC1 6502 1 IC2 62256 1 IC3 27256 1 IC4 MAX232 1 IC5 6850 1 IC6 74LS04 1 IC7 74LS163 1 IC8 74LS93 1 IC9 74LS138 1 IC10 74LS00 1 IC11 74LS02 1 X1 8MHz crystal 1 C1-C5 22uF 16V 5 C6 27pF 1 R1 4k7 1 R2,R3 470R 1 Other Tri-pad Veroboard WireWrap wire 14 pin DIL socket 4 16 pin DIL socket 3 24 pin DIL socket 1 28 pin DIL socket 2 40 pin DIL socket 1 Connectors for power and serial I/O
Back to contents
Wiring required for the data and address buses
Wiring of the decoding, clock and serial interface
Here is the complete circuit of the micro UK101.
The full ROM here is 32K long. Only part of it is actually used and all gaps are filed with FF which means that most EPROM programmers will skip these unused parts very quickly.
Click here to download (zip file)
This ROM consists of BASIC occupying the first 8K and CEGMON occupying the last 2K.
The original BASIC is untouched - it is identical to the original found in my UK101.
The original CEGMON ROM has been patched to allow it to work without needing a dedicated keyboard/screen. Details of the patches applied are shown here.
Pictures of my finished version
A scan of the original CEGMON manual is available here. Please note that the commands relating to text positioning or windows are not applicable as this version is a pure serial interface.
BASIC usage
Connect the microUK101 to a terminal running at 19200 baud, 8
bit, no parity, no handshake.
Ensure CAPS-LOCK is ON on the terminal. Press RESET on the
board and the following message will appear:
Micro UK101 C/W/M?
Press "C". The following message will appear:
MEMORY SIZE?
Press ENTER to allow the full memory to be used by BASIC. After a few seconds the following message will appear:
TERMINAL WIDTH?
Press ENTER. The following messages will be displayed:
31999 BYTES FREE
C O M P U K I T U K 1 0 1
Personal Computer
8K Basic Copyright1979
OK
The computer is now ready for programming in BASIC!
Links to some of my other pages
Build your
own ZX80 - my page showing
you how to build this old micro
|__
ZX80 to
ZX81 conversion - build the NMI generator needed to convert the ZX80 circuit
into a ZX81
|__
ZX80
software - Type in a Space Invaders game into the ZX80
Build your own Jupiter Ace - my page showing
you how to build this old micro
Build your own UK101 - my page showing you how to build
a greatly simplified version of this old micro
Pong - Pictures of
my build of the Atari classic arcade game
My
Machines - My collection of classic 80's micros
I hope this page has been useful.
Grant.
To contact me, my current eMail address can be found here. Please note that this address may change to avoid spam.
Note: All information shown here is supplied "as is" with no warranty whatsoever. All copyrights recognised.
