Motorola 6809

The Motorola 6809 is an 8 -bit microprocessor and further development of the successful also supplied by Motorola model 6800, which was available in various versions from 1978. The combination of the two 8 -bit accumulator register of the processor a processing width of 16 bits is possible in the arithmetic area. The maximum clock rate is 2 MHz, the clock is provided either by a built- in microprocessor or an externally connected clock generator. The latter version is identified by a processor name suffix symbol " E".

Differences for 6800

  • New commands to load effective address in register and to change the contents of registers
  • New commands for affecting the Stacks
  • New page register in order to improve the direct addressing mode
  • Indexed addressing is augmented with new modes
  • 16-bit relative branches could be used to create larger position independent programs
  • 16-bit data processing


It was used among others in several home computers and arcade games, there mostly as a second processor for sound and input control. In addition, he was, for example, Logic Analyzer 1630A/1631A, used by the company HP as standard CPU in screen-based instruments such as the in the signal generators 8115A, 8118A and 8175A, and in the 54200/54201A oscilloscopes and many other instruments. In the manuals of these devices are frequently found also measurement examples and test setups with the 6809th


  • 8 -bit processor
  • 8 -bit-wide data bus
  • Two 8 -bit data registers ( A and B), coupled to a 16 -bit data register ( D)
  • Two 16-Bit-Stapelzeiger/Stackpointer (S and U)
  • Two 16 -bit index register ( X and Y)
  • Support for interrupts (interrupt )
  • First 8 -bit microprocessor having 8 × 8 → 16-bit multiply instruction
  • 59 machine instructions
  • About 6800 transistors

Manufacturers and types of 6809

  • AMS ( Austria Mikro Systeme International) S6809, S68A09, S68B09
  • Fairchild Semiconductor F68B09P
  • Fujitsu MBL68B09E
  • Hitachi HD68B09
  • Motorola MC6809L
  • SGS -Thomson EF68B09J
  • Thomson EF6809P

Pin assignment

The processor was offered in both the 40 -legged DIP/CERDIP- and in the 44 -legged PLCC package