Pi GPIO Output Enable Register

Number	TBRegisterNumber::$90-$93
Readable	TBRegisterReadable::Yes
Writable	TBRegisterWritable::Yes
Short Description	ShortDesc::Enables GPIO pins output

 Bits 27-0: Set bits enable GPIO output on the corresponding GPIO pin (soft reset = all 0)

GPIO pins 1:0 cannot be enabled.

The register $93 is MSB (most significant byte = bits 31-24), register $90 is LSB (least significant byte = bits 7-0).

Bits 31-28 are not explicitly specified in the docs, so consider them "Reserved, preserve current value".