Re: Clone IOU / MMU Chip

["Bryan Parkoff" <nospam@nospam.com>]

"Michael J. Mahon" <mjmahon@aol.com> wrote in message 
JOadnV9AnN_BGTDYnZ2dnUVZ_rXinZ2d@comcast.com">news:JOadnV9AnN_BGTDYnZ2dnUVZ_rXinZ2d@comcast.com...
> David Wilson wrote:
>> aiiadict@gmail.com wrote:
>>
>>>the IOU and MMU are custom logic chips that
>>>select different circuits depending on address
>>>inputs...
>>
>> ....
>>
>>>what else?
>>
>>
>> The IOU & MMU also implement the Apple IIe soft switches used to
>> control video display modes, main vs aux RAM read/write usage, 16K
>> Language card emulation, C100-CFFF ROM space selection, cassette output
>> etc etc
>
> Including pushbutton inputs and annunciator outputs, which are
> very dear to me.  ;-)
>
> Making a feature-for-feature and bug-for-bug clone would be a
> difficult project without more design information.

Michael,

    I agree how difficult is to clone MMU / IOU chips into custom chip.  You 
have to agree with Jim Sather's schematic and diagrams.  If they are 
correct, I would expect custom chip to work by comparing pulse stream using 
Logic Analyzer against IOU / MMU chips.

Rich,

    I appreciate wha you have provided the information.  It is the same what 
it is found in the schematic of Jim Sather.

Bryan Parkoff

Bryan Parkoff