The EMMA and EMMA II SBC’s were produced by LJ Electronics Ltd, Norwich, a company established in 1979 to market training technology to colleges, schools and universities. The company behind LG Electronics still exists but is now known as LJ Create, also carrying the USA based brand Digiac.
Emma, full name MS1 Emma Microcomputer, is a rudimentary 8-bit 6502 processor board, quite similar to the KIM-1 family, with attached hex-input keypad and 7-segment display that was marketed by LJ Electronics in the early eighties. Despite its mere 1K of RAM and 2K monitor in EPROM, it was deemed suitable for driving the Atlas arm. In addition to the processor itself, the Emma range,L.J. Electronics Basic Microprocessor Application System MA02/1, included a large number of sensing, simulation and input-output boards that Emma could be hand-coded to interact with. There was even a mini matrix printer for hard-copy output.
The images below show the Emma processor, keypad and display unit, plus many of the available add-on boards. More complex expansion options included an Eprom programmer and an A4 plotting table. Further capability could be added in the form of the Visa Expansion System – shown above connected to Emma. This added a video interface, 8K of RAM, 8K of BASIC, 6K of assembler and monitor and a full QWERTY keyboard.
EMMA uses a 6502 with a1 MHz crystal, an INS8154 + 74145 RAM I/O IC for 24 keys scanning and 8 seven segment displays, a 6522 VIA for general purpose I/O, 2x 2114 SRAM and a 2716 for the monitor program. A group of CMOS CD4XXX IC’s delivers a Cassette interface
Hardware Manual for the EMMA – 46 pages plus large appendices If ou have it, please help me scan and publish it! I only have three pages as seen in a recent ebay listing:
Emma II was a more compact and complete successor of the Emma. Quite similar, but the keyboard encoding is now done with a 6821 PIA. A VIA 6522 is also present and the usual hex keybaord and seven segment display.
Emma II is well documented (thanks John Evans)
|EMMA II Technical manual in PDF format, including schematics and monitor source, 115 pages.
|EMMA II User manual in PDF format, 109 pages full of experiments.
EMMA emulator by Colin Grey
This is a 6502 simulator. It is loosely based on the LJ Technical Systems EMMA board. Although quite useful it is not a full implementation. Download here.