Eurocom-I and descendants
What is it?
The Eurocom-1 is a computer created by Eltec and is an SBC like the Commodore KIM and Microprofessor. It uses a Motorola 6802 as processor, contains 2 * 2 KB of ROM, 1 KB of RAM plus I/O. I created a new version plus descendants.
Background
In the years 1983 to 1987 I studied at the HTS, technical university (?), in Heerlen (NL) and we used the Labbus, a computer equiped with the 6809. But it was quire new then ther predecessors were still in the training area: the Eurocom-I from Eltec. Some years ago I was given one by Fred Jan Kraan and I decided to dedicate a page to it.6809 CPU
Eltec also created the Eurocom-II, a board equipped with the 6809 CPU.
Anyway, I wanted to document everything of the Eurocom-I, especially the schematic. During creating this page the idea rose to create a better version of it.
A description of the original Eurocom-1
The main features of the Eurocom-I:- Motorola 6802 CPU: same as the 6800 plus 128 byte on board RAM.
- Supports 2 * 2 KB of 2716 EPROM.
- 1 KB of RAM
- 2 * 6821 PIAs, one for the keyboard and displays, one free one.
- one cassette port with a 6850 ACIA as core part.
- Two 64 pin AC-DIN connectors.
- RAM at $A000, I/O at $8000.
- A 4020 counter is used as interrupt generator.
My idea of the Eurocom-1
- As above, the same 6802 CPU.- 2764 8 KB EPROM but only 6 KB wil be used. Using a 2764 also means I can use a 27C256 EEPROM.
- Needing up to 56 KB of RAM, I chose for using a 128 KB RAM. Main reason: I only need one IC.
- The cassetteport is removed but the ACIA is kept. A 1,8432 MHz oscillator replaces the original clock generator. A header is added for the typical RS-232 signals but I'll use them only in digital form.
- The 4020 is replaced by a 74LS393.
- A GAL is used to choose the addresses for the ROM, RAM and I/O. Advantage: the configuration can be changed when needed.
- Yo be able to make use of the various Elektor cards I own, I added a 64 pins male AC DIN connector. This enables me to connect an expansion bus from the left site of the board, which on its turn enable me to connect various Elektor expansion boards like the RTC, Floppy controller and video card.
I created a schematic and board but they so much the same as the ones of the Eurocom6809
The Eurocom6809
The creation of the schematic was relatively simple: just replace the 6802 with a 6809. The 6809 does not have a VMA line but it could be created with some gates. The MicroKit09 does only use the E signal to synchronize the CPU with the ROM, RAM and I/O and I have living proof that that works fine. So I decided to keep it simple and drop the VMA line completely.The schematic:
The board:
The software
I cannot use the software of the original Eurocom-I as it written for the 6802 CPU.The German magasine CHIP published in November 1983 an article about this 6809 board including the hex listing of the ROM. I tried to OCR the article but in the end I had to type in everything by hand, just like the "good" old days. I tried to disassemble it but I ran into a weird problem: there were calls pointing to the address $FC1C but that was in the middle of an instruction. The weird thing, various jumps, branches and instructions pointing to addresses above and under the address $FC1C were OK. Another problem: having the instructions does not mean everything is clear.
So I decided for another solution: I will use the prooven software of the new software for MicroKit09. I have to expand it a bit as it has more keys.
The EurocomSC/MP
This verion is based on National Semiconductor's SC/MP, also named INS8060. This one took quito some more effort because it needed an extra IC, a 74LS75 4-bit latch, to generate the address line A12..15. Schematic and board are available if needed.The Eurocom6502
The name already says it, this one is based on the well known MOS 6502. Converting the schematic and board took less than hal an hour.The Eurocom6502B
The above board is taken as base but now the 6821s have been replaced by 6522s.The software
As I have no idea if I will build the boards yet, I haven't even started about thinking about the software. For the SC/MP alone I would already have to build my own assembler and disassembler.The EurocomZ80 or other versions
I have indeed thought about a Z80 but then I decided against that one. Reason: I have the MicroProfessor-1B and 1P that fill that niche. The only processors that comes to my mind right now could be the 1802 and 8085.You can email me here.