[sdiy] Xpander

[Roman Sowa]

No, because Matrix12 halts the voice processors using HALT pin, and then 
mingle their RAM. All 3 run on the same clock, which is distributed from 
main CPU to voice boards via long shielded cable, that can easily pop 
out of the socket if you drop the unit few times. Halt anc clock 
discontinuities are sometimes the reasons for unpleasant welcome message 
and freezed state. Same thing applies for Xpander obviously.
One nice feature I like and admire about matrix12 is the hardware 
keyboard encoder, that is about 10x10'' sized board, full of logic 
chips. Very fine velocity resolution, IRC 64us steps and 12-bit deep count.

Roman

W dniu 2020-10-18 o 22:43, Richie Burnett pisze:
> With shared RAM between multiple CPUs don't you then have to implement bus arbitration to prevent collisions?
>
> High speed UART or SPI seems simpler to me.
>
> -Richie,
>
>
> Sent from my Xperia SP on O2
>
> ---- Tom Wiltshire wrote ----
>
>>> On 18 Oct 2020, at 21:07, Gordonjcp <gordonjcp at gjcp.net> wrote:
>>>
>>> On Sun, Oct 18, 2020 at 12:20:00PM +0100, Tom Wiltshire wrote:
>>>> The Prophet T8 worked the same way, with the main processor writing to a common RAM area shared with the voice (“final”) processor.
>>>>
>>>> Given the speed of serial comms at the time, it makes a lot of sense. In many ways it *still* makes a lot of sense.
>>> I don't know, the Juno 106 communicates between the main CPU and the voice CPU at MIDI speeds but with only two-byte messages.
>>>
>>> Nobody's ever accused the 106 of being laggy.
>> Fair enough. The truth is that humans are really slow, so parameter updates don’t have to be that fast. As long as those note on/off messages get through in a timely manner, probably no-one will notice.
>>
>> Still, parallel comms is always going to be faster, and I like the “transparency” of using a shared RAM to get data from one system to the other. It’s quite neat, in a rather 1980’s way!
>>
>>
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