Motorola 6800

Motorola 6800

The 6800 was an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface ICs, RAM, ROM and other support chips. A significant design feature was that the M6800 family of ICs required only a single five-volt power supply at a time when most other microprocessors required three voltages. The M6800 Microcomputer System was announced in March 1974 and was in full production by the end of that year.

The 6800 architecture and instruction set were influenced by the then popular Digital Equipment Corporation PDP-11 mini computer. The 6800 has a 16-bit address bus that could directly access 64 KB of memory and an 8-bit bi-directional data bus. It has 72 instructions with seven addressing modes for a total of 197 opcodes. The original MC6800 could have a clock frequency of up to 1 MHz. Later versions had a maximum clock frequency of 2 MHz.

In addition to the ICs, Motorola also provided a complete assembly language development system. The customer could use the software on a remote timeshare computer or on an in-house mini-computer system. The Motorola EXORciser was a desktop computer built with the M6800 ICs that could be used for prototyping and debugging new designs. An expansive documentation package included datasheets on all ICs, two assembly language programming manuals, and a 700-page application manual that showed how to design a point-of-sale computer terminal.

The 6800 was popular in computer peripherals, test equipment applications and point-of-sale terminals. The MC6802, introduced in 1977, included 128 bytes of RAM and an internal clock oscillator on chip. The MC6801 and MC6805 included with RAM, ROM and I/O on a single chip were popular in automotive applications.