Microvision

The Microvision was a hand-held game console released by Milton Bradley Company in 1979. The Microvision was designed by Jay Smith who later went on the design the famous Vectrex. Microvision's combination of a cartridge-based system and portability would surely be a success. In the first year, $8 million was grossed making Smith Engineering a million dollar industry. But very few cartridges, a small screen, and no backing-up by a conventional console lead to its demise in 1981.

Microvision units and cartridges are very rare nowadays. Time is taking its toll on the Microvision units still in existence. There are three main problems faced by Microvision owners: screen rot, ESD damage, and keypad destruction.

The manufacturing process used to create the Microvision's LCD was primitive by today's standards. Poor sealing and impurities introduced during manufacture has resulted in a condition known as screen rot. The liquid crystal spontaneously leaks and permanently darkens, resulting in a game unit that still plays but is unable to properly draw the screen. While extreme heat (such as resulting from leaving the unit in the sun) can instantly destroy the screen, there is nothing that can be done to prevent screen rot in most Microvisions.

A major design problem involves the fact that the microprocessor (which is inside the top of each cartridge) lacks ESD protection and is directly connected to the copper pins which normally connect the cartridge to the Microvision unit. If the user opens the protective sliding door that covers the pins, the processor can be exposed to any electric charge the user has built up. If the user has built up a substantial charge, the discharge can jump around the door's edge or pass through the door itself (dielectric breakdown). The low-voltage IC inside the cartridge is extremely ESD sensitive, and can be destroyed by an event of only a few dozen volts which cannot even be felt by the person delivering the fatal shock.

Instead of having buttons on a separate controller, the Microvision unit had a nine-button keypad, with the switches buried under a thick layer of flexible plastic. To align the user's fingers with the hidden buttons, the cartridges had cutouts in their bottom (over the keypad). As different games required different button functions, the cutouts were covered with a thin printed piece of plastic, which identified the buttons' functions in that game. The problem with this design is that pressing on the buttons stretched the printed plastic, resulting in the thin material stretching and eventually tearing. Having long fingernails exacerbated the condition.

The first Microvision cartridges were made with both Intel 8021 and Texas Instruments TMS1100 processors. Due to purchasing issues, Milton Bradley switched to using TMS1100 processors exclusively. The TMS1100 was a more primitive device, but offered more memory and lower power consumption than the 8021. First-revision Microvisions needed two batteries due to the 8021's higher power consumption, but later units (designed for the TMS1100) only had one active battery holder. Due to the high cost of changing production molds, Milton Bradley did not eliminate the second battery compartment, but instead removed its terminals and called it the spare battery holder.

Microvision in the movies: A Microvision appears in the movie Friday the 13th Part 2 (http://www.imdb.com/title/tt0082418/).

Technical Specifications

• CPU: Intel 8021/TI TMS1100 (on cartridge)
• Screen type and resolution: 16 x 16 pixel LCD
• Register width: 4 bit (TMS1100), 8 bit (8021)
• Processor speed: 100 kHz
• RAM: 32 nibbles (16 8-bit bytes, integrated into CPU)
• ROM: 2K
• Cartridge ROM: 2K masked (integrated into CPU; each game's CPU was different)
• Video Display Processor: Custom (made by Hughes)
• Sound: Piezo beeper
• Input: Nine button keypad, one paddle
• Power requirements: One 9 volt battery (TMS1100 processors), Two 9 volt batteries (Intel 8021 processors)

Complete list of Microvision game releases

• Block Buster (1979)
• Bowling (1979)
• Connect Four (1979)
• Mindbuster (1979)
• Pinball (1979)
• Star Trek Phaser Strike (1979)
• Vegas Slots (1979)
• Baseball (1980)
• Sea Duel (1980)
• Alien Raiders (1981)
• Cosmic Hunter (1981)
• Barrage (1982)
• Super Blockbuster (1982)

External links

• Microvision FAQ 1.2 (http://users2.ev1.net/~rik1138/MB/MicrovisionFAQ.txt)