Re: DMA successes with Verilog

From: Jim Brain <brain_at_jbrain.com>
Date: Thu, 14 Jun 2018 21:07:38 -0500
Message-ID: <df75c1ad-e347-ff25-9d6a-c160a0033e94@jbrain.com>
On 6/14/2018 4:29 PM, Mia Magnusson wrote:
>
> Why does the badlines work while you supposedly cant DMA any time you
> want? (Assuming DMA is synchronised to the clock)?
DMA is sync with PHI.

Not sure your question, but badlines are when the VIC-II essentially 
uses the CPU slice of the clock cycle for it's own use.  Because it is 
doing so, it's a badline, and neither the main CPU or any DMA activity 
can use that slice.
>
> Anyways if you really want to know what the CPU is doing you could
> watch the buses. More than two accesses to concecutive addresses means
> that it is fetching from program, i.e. instructions or operands.
I don't think that's true.  a piece of code that reads data from it's 
own space would trigger the same rule.
> Then
> it would be easy to see when it accesses some place else, that must be
> data. Backtrace the data bus a bit and then you can be sure where that
> instruction started and where it will end.
I have faith that if there were easier ways, Gideon would have found and 
implemented them.
Received on 2018-06-15 05:00:17

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