Ideas for a simple, but somewhat extendable computer bus

allison allisonportable at
Mon Nov 20 06:49:13 CST 2017

On 11/19/2017 10:51 PM, Eric Smith wrote:
> On Nov 19, 2017 7:18 PM, "allison via cctalk" <cctalk at
> <mailto:cctalk at>> wrote:
>     The rest is the specific implementation.  What happens if the CPU is
>     1802 or something else that does not match the 6500 or 8080z80 models.
> There is nothing that prevents either the serial or parallel
> arbitration schemes from working with other processors.
Understood but not always easily applied.

> In the case of the 1802, it would work easily for interrupts, but
> would need some additional circuitry for DMA, because the 1802 doesn't
> include any feature whereby another bus master can request that the
> 1802 surrender control of the bus. Instead, the 1802 has a built-in
> single-channel DMA controller.
Its why I picked that one.

> That 1802 bus master problem exists for interfacing _any_ sort of bus
> master to any 1802, and is totally independent of what kind of DMA
> arbitration is chosen.
True, but as a potential candidate on a generalized bus how do you
handle that, besides wait states
or processor clock stall? Of course being CMOS its easily done at a cost
of performance.

All of this is targeting a generalized bus to run a large selection of
cpus possibly mixed with radically different bus cycles.


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