Re: How hardware accelerators deals with $0/$01

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Thu, 19 Oct 2017 22:22:44 +0200 Message-ID: <843fddb4-56a2-8861-350b-844833a55433@laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 10/19/2017 10:03 PM, Mia Magnusson wrote:
> 
> Are we sure that the 6510 I/O port isn't accessible from external
> hardware when the CPU is in DMA/three state mode?

Yes... The address lines of the 6510 are output only, same for the R/W 
line. Also an access by the 6510 to $00 and $01 does not appear on the 
address and data bus.

So the only circuit that can control the I/O lines of the 6510 is the 
6510 itself.

  Gerrit

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