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the_mill_daughterboard
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Luca Ridarelli 2017-01-16 20:27:01 +01:00
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@ -3,12 +3,12 @@ APPLE ][ Stellation Two "The Mill" 6809 OS/9 daughter-board PCB and Prom code.
DESCRIPTION
This project contains schematics and software of a plug-in daughter-board for the APPLE ][ Stellation Two "The Mill" 6809 OS/9 card.
The daughter-board remaps Apple II ram as seen by the 6909 board to allows execution of Microware OS/9 .
The daughter-board remaps Apple II ram as seen by the 6909 board to allow execution of Microware OS/9 .
This is not the original implementation of the Stellation Two daughter-board nor a clone of it.
The original daughter-board made use of one 74S288 prom and 74LS367 Hex Buffer to create a custom memory mapping.
The high cost of 74S288 prom burners and scarce availability of 74S288 proms suggested to implement a different solution.
The high cost of 74S288 prom burners and the scarce availability of 74S288 proms suggested to implement a different solution.
Then one ATmel ATF16V8C PLD has been programmed to emulate a prom with the right ram memory mapping combination.
A switch has been added to allow for normal/OS9 memory mapping selection.