The EurocomTMS7000

What is it?

The design is based on Eltec's Eurocom-I or better, version C of the Eurocom6502. I started with the TMS70C02 version after the 6502C version and saw no reason at all starting with a re-design of the original Eurocom-1 one and so on.

This version is equipped with the TMS70C02. I'm not familiar with this CPU at all. If I want to program with it, I need to update my assembler and disassembler to include the TMS70C02. Yes, there are other assemblers around but having your own one is half of the fun.

The TMS7000 family uses a multiplexed data-address bus, just like various Intel ICs. That means an extra IC when compared with the original design. On the other hand the TMS70C02 has an onboard serial port. Just input and output, no handshake lines. But more than enough IMHO.

On internet I only found a few designs, ones with only a few KB of RAM. What worried me was the fact that in all cases the memory map was split up in ROM, RAM and I/O and all ranges were completely decoded. If using, let's say, 56 KB of RAM, I was not in the mood decoding the whole address range so I could free the very first 256 bytes for internal use. The Motorola 6802 has 128 bytes onboard but when connecting, for example, 32 KB of RAM, one has not to decode these 128 bytes out of the address range; the 6802 simply ignores the data bus when accessing these 128 bytes.
I studied the TMS7000-family data book and I'm quite sure I found the two parts that state that the TMS70C02 does behave the same. I give the design to two friends with a lot of TMS experience and await their verdict.

The successor

I also have a successor based on this design. There are two relatively big changes:
- The display is replaced by a LCD screen.
- The keyboard is replaced by a connector connected to the 6522, capable of handling a Commodore 64 key board and an AtMega328P plus PS/2 keyboard connector. The AtMega328P, known for being used on the Arduino UNO R3, converts the PS/2 keyboard code into 8-bit ASCII code plus handshake, to be read by the same 6522. Which keyboard to use depends simply on which parts you install. And the software of course.

Name, schematics and board will follow.

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