This page contains the details of a project being undertaken by David Fry and me to build a modern version of the Microtan 65 system.
Many of the items developed are available for purchase at the shop here
The PCBs are being developed using KiCad (kicad-pcb.org).
The KiCad project files have been archived in the ZIP files in the relevant sections below and include the Gerber files for PCB production.
Bare MT65-R CPU v1.0b PCBs are available for sale in the Shop
Character Generation EPROM
The character generator map is burned into a 4k (2732) EPROM with either the upper 2k being the inverse (Rev1).
Rev 1 code Binary Image
or with the upper 2k being identical to the lower 2k (Rev2).
Rev 2 code Binary Image
Note: The FORTH programs require Rev2 code for its 'Words' to be displayed correctly. This is
because the 6502 code stores Words with the 8th bit of the last character set to denote the end of the word.
Note: TUGBUG cannot be used with a MT65-R CPU board in Single Board configuration
(ie with the 3 links closed and no TANEX). Explanation here
This is a modern replacement for Tangerine's Tanex card.
It is fully compatible with the original and has the following specification:
A single AS6C1008 (128kx8) SRAM chip providing 64K memory ($400-$EFFF addressable).
2 x 27512 EPROMs providing 8 pages of 12K EPROM to overlay $C000-$EFFF RAM memory space.
A single (user-selectable) IO memory location provided for selecting EPROM Memory Page
to overlay $C000-$EFFF memory space or to leave this space as RAM. Default is EPROM Memory
Page 0. LED indication of selected memory bank.
2 x 16V8 GAL chips used for SRAM addressing and EPROM port addressing/bank selection.
2 x 6522 VIAs unchanged providing 4 parallel ports. Four 8 x 2 IDC Header connectors
to be used.
UART 6551 unchanged providing TTL level RS232 serial IO. Full 'true' RS232 level serial IO
also provided by MAX238 chip - selection by jumper. IDC Header connector to be used.
(Note: 20mA Loop circuitry is not retained)
Cassette Tape interface using 2 x LM358 but using Oric Tape interface design.
5 way 180 deg DIN socket connector (same as on Micron Front Panel).
Data buffering using 2 x 74LS244 chips.
Accepts TANBUS DMAREQ signal and drives TANBUS DMAGNT and ABE signal lines. Generates TANBUS ROME, RAME and IOE signals.
Note: UART 6551 may be substituted with 65C51 in PCB versions 1.0b and above.
This is a modern replacement for the Tangerine High Resolution Graphics (HRG) board.
Provides 256x256 pixel high resolution graphics screen. When used with the
HRG Toolkit can also provides a 51 character x 45 line high-resolution text screen.
Modulated UHF and composite video outputs available.
Bare HRG v1.0b PCBs and programmed Toolkit EPROMs are available for sale in the Shop
This is modern replacement for the Bulldog Soundcard. It includes a battery backed Real Time Clock module.
The PCB design, Manual and supporting software were developed by James Price. It has the following specification:
A double sided PCB suitable for use with a Microtan-R backplane.
3 voice sound as default and a further 3 voices available as an option.
Audio waveforms provided by the AY-3-8910 sound chip.
Onboard 300mW LM386 based audio amplifier and integral speaker including volume control.
Optional components to increase amplifier gain if desired.
Line level output.
Optional battery backed highly accurate (5ppm) Real Time Clock (RTC).
Optional 32Kbit EEPROM memory.
16 (32) general purpose I/O ports.
Optional system Power On Reset function.
Header pins for I2C and RTC expansion / monitoring.
Audio, RTC and EEPROM memory functions are programmable / controllable from BASIC and
The addresses occupied by the sound card within the Microtan memory map are configurable.
SNDEMO.txt - Sound demo program in BASIC RTCBAS.txt - RTC demo program in BASIC2 RTCHYB.txt - RTC demo program Machine code core + BASIC wrapper EEPBAS.txt - BASIC Test program for the EEPROM chip on the RTC
module MC2DAT.txt - BASIC program for converting bytes in memory to BASIC
DATA statements i2c_asm_mt.asm - Assembly source file for the RTC machine code routines i2c_lst_mt.lst - Assembled listing for RTC machine code routines
Because of the size of the associated .wav files, they are held on my FTP server. If you wish to download any of these files, please send me an email (address is on the Home page) and I will provide access information. All .wav files have been saved at 'FAST' speed.
James has also been experimenting using the soundcard as a musical instrument. He has generated a document that captures the various steps he has taken.
The associated software files are also available on my FTP server.
What started life as a bespoke 19 inch 4U system rack has been modified to accommodate the Microtan
Circuit Boards and fit into my existing Vero 19 inch enclosure.
This involved removing the end plates, cutting them down to size and re-drilling the holes for the screws
that hold the 6 longitudinal rails in place.
The motherboard has been designed to accommodate CPU, TANEX and 5 expansion slots.
The slots are 1 inch apart to allow for a wider PCB form factor and increased cooling.
Tanbus expansion slot signal lines 19b and 19b have been earmarked for Video1 and Video2 signal.
Each may be configured by on-board jumpers to link to Tanbus CPU slot signal lines 20a or 20b.
The first production run has been completed and one of the first-offs has been installed in the System Rack.
This is being used to test and repair a number of Microtan boards.