Lawrence Livermore Laboratory MST-80B

Lawrence Livermore Laboratory MST-80B

The LLL MST-80B is a complete microcomputer system self-contained in a briefcase for portability and easy usage. The microcomputer was designed as a training device for LLL’s Technology Training Program (TTP), and lowing students to explore the hardware and software capability of a typical microcomputer.


The trainer uses the Intel 8080A Microprocessor and supporting integrated circuits. It has its own set of solid-state memory elements so no external memory is required. Both random-access read/write memory (RAM) and programmable read-only memory (PROM) are provided. The MST-80B has a 24-key keyboard and a 3-digit numerical display for the student to communicate with the microcomputer. This input/output (I/O) combination eliminates the need for expensive and bulky I/O such as a teletypewriter. The keyboard and numerical display can be used with either the octal (base 8) number system or the hexadecimal (base 16) number system. Either number system can be selected by simply depressing a control key. The trainer includes a breadboard socket so that experiments can be interfaced to the microcomputer through an 8-bit input port and an 8-bit output port. This allows the student to learn hardware Interfacing techniques as well as software programming. The MST-80B also has ten uncommitted light-emitting diodes (LEDs) that can easily be connected to display the state of any desired signals (address lines, data line and status). These can be used when operating the trainer in the single-step mode or the normal operating mode.



  • 512 bytes o f RAM memory.
  • Sockets for three 1702A PROM’s (768 bytes). It also includes one uncommitted socket that can be jumper-wired to 24-pin ROM ofuser’s choice. Normally, the Monitor Program resides in PROM 0 and PROM 1.
  • A 24-key keyboard. This input device is accessed through memory mapped I/O.
  • A three-digit display with full, hex-number capability. This output device is used by calling the DISPLAY subroutine in the Monitor.
  • One 8-bit input port. Address = 1.
  • One 8-bit output port (latched)., Address = 1.
  • Single-step capability.
  • Ten uncommitted light-emitting diodes (LEDs) that can easily be connected to display the state of any desired signals (address lines, data lines, status, etc.). These can be used when operating in single-step mode.
  • A self-contained power supply.
  • A self-contained power supply.

Have now backed up the 1702A PROMs’ and  burnt new ones.

The Programmer I made from a kit and used.

Demo of a Counter program in the manual running from RAM with LED’s connected to the I/O port.

Have now burnt the Demo counter program to PROM1. Changed the program so it counters up to FF and stops then flashes the LED’s


The Manual and Schematic to download from the links below. I’ve got copy’s of the PROM hex files if anyone needs them just contact me.



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