Some Timex models, like Timex Sinclair 2068 and Timex Computer 2068 provided slot for cartridges.
The slot has following 36 lines:
- power: GND and +5V,
- address lines - A0..A15 and separately A7 with 7th refresh bit - A7R,
- data lines - D0..D7,
- Z80CPU control signals: /RD, /WR, /MREQ, /IORQ, /M1,
- active low chip select signal for Dock bank - /ROSCS,
- active low chip select signal for EXROM bank - /EXROM - useless, as there's no easy way to disable internal EXROM memory,
- in TS2068: memory refresh signal - /RFSH of Z80, or
in TC2068: active low chip select signal for Home ROM - /ROMCS (also useless),
- in TS2068: active low memory access disable - /BE of ULA, or
in TC2068: active high input that disables both internal ROM and also forces high state on both /ROMCS and /EXROM in the slot.
Due to the incompatibility and useless signals placed in the slot, the safest way is to build Dock cartridges (using /ROSCS) and I/O cartriges only.
Design of safe Home or EXROM cartridge would require a duplication of #F4 and #FF ports. Anyway, in each 2068 model the memory is disabled in other way (low or high state).
Universal Memory Cartridge Board
The UMCB is kind of universal board that can be used to build wide range of memory cartridges. Memory is seen in Dock only for Timex Sinclair 2068. For Timex Computer 2068 it is also possible to build Home ROM cartridge. It is not possible to make an EXROM cartridge without internal changes.
Amount of memory accessible by Z80 is limited to 64kB, as the board doesn't support bankswitching. An extra board with bankswitching can be installed under the memory chip (e.g. FlashD0 or 512kB SRAM upgrade).
|23128||16kB of PROM. For example ROM chip from ZX Spectrum 48K.|
|2732||4kB of EPROM.|
|2764||8kB of EPROM.|
|27128||16kB of EPROM.|
|27256||32kB of EPROM.|
|27512||64kB of EPROM.|
|27C010||128kB of EPROM. Only 64kB seen at a time.|
|---- Larger EPROMs skipped. ---- |
|28C16||2kB of EEPROM, reprogrammable at +5V.|
|28C64||8kB of EEPROM, reprogrammable at +5V.|
|28C256||32kB of EEPROM, reprogrammable at +5V.|
|28C512||64kB of EEPROM, reprogrammable at +5V.|
|29F010||128kB of PEROM, reprogrammable at +5V. Only 64kB seen at a time or switched with OUT port on extra board (FlashD0).|
|---- Larger EEPROMs skipped. ---- |
|6116||2kB of SRAM.|
|6264||8kB of SRAM.|
|62256||32kB of SRAM. Two such chips can be used to get 64kB RAM: one must be in 0.3" case, second in 0.6" case. Also, when SRAM is 0.3" wide, the second chip can be any type of ROM.|
|628128||128kB of SRAM. Only 64kB seen.|
|628512||512kB of SRAM. Requires extra board with bankswitching.|
Two memory chips mode
The UCMB can contain also two memory chips, as long as one of them is in 0.3" case - in most cases this is 62256 SRAM (32kB, used as cache in PC). Such cardrige can be used to run ZXVGS FD0 (with extra FlashD0 board) or CPM22QED UPB.
The decoder used is 74*253 or 74*153, so provides two /CS signals for each chip separately. In some special case it can be replaced with 74*138 (e.g. only 4kB of Home ROM replaced in Timex Computer 2068).
UMCB version v001
This is first suggestion for the board. Dimensions 48mm × 48mm (below the horizontal dashed line) are taken from original board used in Spectrum Emulator for Timex Computer 2068. The round hole (10mm) is made to give a chance to remove the board when no case is used. There are two problems with insertion into TS2068: the cartridge slot has limited hight and it could be hard to remove the 48mm board from the cased slot. So, to locate the memory chip outside the limiter, a 30mm lengthener was added (over the horizontal dashed line). It can be cuted out, giving a 48mm × 48mm board. In this case a female slot can be mouted on the cuted part, giving a free lengthener or cartridge splitter.
UMCB version v003
These boards have more options than v001. There's place for reset button, pads for signals like /EXROM, /IORQ, etc. Without modifications (just by soldering chips), the board can be used as:
- ZX Spectrum Emulator in Dock - 16kB PROM, seen in first 16kB (use OUT 244,3 to select it),
- 32kB LROS - 27128 or 27256, seen in first 32kB of Dock,
- 32kB RAM - 0.3" case 62256, seen in second 32kB of Dock,
- 32kB RAM - 0.6" case 62256, seen in first 32kB of Dock,
- 64kB RAM - two 62256, cases 0.3" and 0.6", seen in whole Dock,
- 32kB RAM + 32kB ROM - 0.3" case 62256 (second 32kB of Dock) and 27256 (first 32kB of Dock).
Files for download
- 0006a.jpg 165.0kB (2006-11-15 16:06), uploaded by Jarek Adamski
- Cartridge of 64kB SRAM in Dock for Timex 2068. The top 32kB is in socket, so this can be used e.g. to read EPROMs or program 28C64 EEPROM.
- umcb-zx2.jpg 31.2kB (2006-08-02 16:57)
- Two mounted "ZX Spectrum Emulator" cartridges. View 2. Original ZX Spectrum PROM is used.
- umcb-zx1.jpg 31.5kB (2006-08-02 16:57)
- Two mounted "ZX Spectrum Emulator" cartridges. View 1. Original ZX Spectrum PROM is used.
- 900505.zip 29.5kB (2006-05-12 04:43)
- Board of Spectrum Emulator for Timex Computer 2068. Eagle data files.
- spectrum.jpg 82.0kB (2004-07-14 01:27)
- Original Spectrum Emulator cartridge for Timex Sinclair 2068. Case top view.
- zebra.jpg 29.0kB (2004-07-14 01:27)
- TS2068 Spectrum ROM Cart by Zebra Systems. Board top view.
Links to other pages
- Timex 2068 : 128kB ROM + 512kB RAM
- Internal memory upgrade for Timex Sinclair 2068, Timex Computer 2068 and Unipolbrit Komputer 2086. 128kB ROM, extra 512kB RAM.
- Dock bank : Timex
- The 64kB memory bank known from Timex computers. Timex memory map.