Hardware

The mission of the MC is to provide the intelligence to the system. This unit contains the microprocessor (Zilog Z80), the first 24 KB of memory (8KB EPROM + 16KB RAM), and logic for coordinating INT and DMA requests asserted by external devices throughout the EXT-BUS.

A DSUB-37 connector is present in the rear to expose the EXT-BUS being this the only way out for the MC. In the front, a "traditional" Control Panel (Console) is offered to the Operator for machine control and software debugging.

A professional open-reel 1/4 inches Stereo Audio Tape Recorder OTARI MX-5050, without modifications, will be utilized as data Tape Drive for the LC-81 minicomputer. A controller equipment (namely "Tape Controller") will serve as interface between the two. The Controller will connect to the LC-81 via EXT-BUS, and it connects to the OTARI via audio cables and a special control cable.

The OTARI MX-5050 is very generous in terms of control. It offers a DB37 connector in the rear, labeled "Parallel I/O", with GPIOs for asserting and tallying virtually all machine operations such as Play, Record, Rewind, etc. Also in the Parallel I/O connector is a 9.6 KHz reference pulse and also the output of the Tachometer (120 pulses per second at nominal speed).

The resulting equipment will be a Tape Drive entirely controlled by software running at the LC-81 and complaint with the LC-81 Tape Drive Specification (see section "Specs").