Motorola 6809

A Motorola 6809

Chip photo of a Motorola 6809 (MC68B09L)

The Motorola 6809 is an 8- bit - microprocessor and further development of the successful coming also from Motorola model 6800 , which was available in different versions from the 1978th By combining the two 8-bit accumulator registers of the processor, a processing width of 16 bits is possible in the arithmetic area. The highest possible clock rate is 2 MHz, with the clock being provided either by a clock generator integrated in the microprocessor or by a clock generator that can be connected externally . The latter version is identified by an abbreviation "E" after the processor designation.

Differences to the 6800

Instructions to load effective addresses into registers and to change the contents of registers
Commands for influencing the stack
New page register to improve the direct addressing mode
Indexed addressing has been expanded to include new modes
Relative 16-bit branches could be used to create larger, position-independent programs
16-bit data processing

use

It was used, among other things, in some home computers such as the Dragon 32, Dragon 64 and arcade slot machines , there mostly as a second processor for sound and input control. It was also used in the Vectrex game console .

Furthermore, it was installed by HP as a standard CPU in screen-based measuring devices such as the Logic Analyzer 1630A / 1631A, in the signal generators 8115A, 8118A and 8175A, as well as in the oscilloscopes 54200 / 54201A and many other measuring devices. The manuals for these devices often also contain measurement examples and test setups with the 6809.

Technical specifications

8-bit processor
8 bit wide data bus
16-bit address bus (64 kB memory addressable)
Two 8-bit data registers (A and B), can be coupled to form a 16-bit data register (D)
Two 16-bit stack pointers (S and U)
Two 16-bit index registers (X and Y)
Support for interrupts ( interrupt )
First 8-bit microprocessor with 8 × 8 → 16-bit multiplication instruction
59 Machine commands
Approx. 9000 transistors