Retrocomputing Stack Exchange
Retrocomputing Stack Exchange

Questions tagged [6809]

For questions regarding the Motorola 6809 microprocessor.

The 6809 was designed by Terry Ritter and Joel Boney at Motorola's Austin Texas facility.

It can be considered a second generation 8 bit microprocessor built by studying the short falls and programming experiences from the 6800 line of chips.

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What limited the use of the 6809 CPU in personal computers?

Why did manufacturers of home computers avoid using the 6809 CPU? I realize that the Z80 and 6502 had a 3- or 4-year head start in availability. But once it did become available in 1978, I don't understand why designers of new computers didn't…
RichF
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Advantages of a Hitachi HD6309 versus a plain Motorola MC6809

Hitachi was a second source for the Motorola 6809 Micro Processor. The 6309 had many secret features. What advantages does the HD6309 have over the MC6809?
tlindner
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Motorola 6809 Stack Blasting

I've seen several mentions of a "Stack Blasting" technique for copying memory quickly on the 6809. What is it? How does it work?
tlindner
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Why did MC6809(E) require two-phase clock consisting of two square waves shifted by 90°?

Usually when talking about two-phase clocks in early CPUs, one means this type of clock, that consists of two non-overlapped pulses. Examples are MC6800 clock (page 3) or i8080 clock (page 6). Many ICs generate such clock phases internally from a…
lvd
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How to use rounding with 6809 multiplication

The MC6809 is unusual for an 8-bit processor of its era in having a hardware multiply instruction. MUL multiples the 8-bit unsigned integer in the A register with the 8-bit unsigned integer in the B register, leaving the product in the 16-bit D…
Wayne Conrad
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HD63B03R timer interrupt frequency

I am trying to maintain an old procuct for my employer, based on an HD63B03R which is a 6800-style micro. The crystal on the PCB generates a 4.75MHz clock. I believe from the data sheets found on t'internet for this device thet the CPU internally…
GEphil
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