View source for NextPort:$FF3B

{{Port
|Number=$FF3B
|ShortDesc=ULA+ Data
|Readable=Yes
|Writable=Yes
}}

(R)

If palette group is selected, the palette value stored at the current ula+ palette index is returned
If the mode group is selected, bit 0 = 1 to indicate ULA+ is enabled

(W)

If the palette group is selected, a palette value is written to the current ula+ palette index
If the mode group is selected, bit 0 = 1 to enable ULA+, 0 to disable ULA+

For ULA+ i/o ports, all colours are read and written in 8-bit format GGGRRRBB.  The 9th blue bit is automatically generated
as the logical OR of the two other blue bits.