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External Hardware IO Address Map

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External Hardware IO Address Map

Tandy designated IO addresses from $FF60 to $FF7F for add-on hardware, but several parties chose to build in the $FF40-$FF5F and $FF80-FF8F ranges as well. Here are known IO addresses for add-on hardware.

Note some devices overlap each other; these devices will conflict and cannot be used together without modification.

Built-in IO devices (such as the PIAs ($FF00-FF3F), CoCo3 GIME ($FF90-FFBF), and SAM ($FFC0-FFDF)) also take the IO space. The 6809/6309 CPU uses $FFF0-FFFF for interrupt vectors.