Re: 6510 I/O port as chip selects to expand memory

On 11/18/21 12:55 PM, Frank Wolf wrote:
> The 7501/8501 used in the C264/plus4 series sacrificed one of the port 
> bits internally to add the infamous GATE_IN logic.
> 
> The rest of the chip layout is identical to the 8500 (==6510).
> 
> Here's a solution which uses a 6502 instead of the 6510 to mimic the 
> 8501 functionality:
> 
> https://gitlab.com/toms01/6502a_or_w65c02_at_8501

The annoying part of the 6510 ist that they left out P6 and P7. When you 
want to use this port for IO, having Bit 6 and 7 makes certain things 
way easier since you can work with the BIT command of the 6502 which 
will transfer those 2 Bit into the status register, allowing you then to 
directly use branch commands.

  Gerrit