ULA Control Port

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Number $xxFE
Short desc. Controls border color and base Spectrum audio settings.
Bit Mask %---- ---- ---- ---0
Readable No
Writable Yes

When written to, adjusts the border color and audio devices as follows:

Bit Function
0-2 Border color
3 Enable MIC output
4 Enable EAR output
5-7 Unused

Reading the port with certain particular high bytes will read the keyboard - see Keyboard ($**FE / 254). Bit 6 of the ULA byte is always the EAR input.