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Book created: 03-12-2017

This section describes the computer's hardware in great details including theory of operation and schematics of the different LC-81 units.

Click to selectMaster Controller Unit (MC)

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.

Click to selectOpen-Reel Tape Drive
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").
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