ZEsarUX ZXI Port register: 53051 (CF3BH)
ZEsarUX ZXI Port data:     57147 (DF3BH)

To write a register, first OUT to port register 0xCF3B and then OUT to port data 0xDF3B
To read a register, first OUT to port register 0xCF3B and then IN from port data 0xDF3B
You can also read the register selection doing a IN from port 0xCF3B
Port register 0xCF3B is set to zero when doing a reset



There are 256 possible registers:


* Reg 0: CONTROL_BITS0. Set to 0 when doing a reset

Bit 0: Set to 1 to map lower 16kb inves memory ram readable from 0000-3fffh
Bits 1-7: Unused


* Reg 1: HARDWARE_DEBUG_ASCII

Write this register to output an ascii character to the pc console. Must be enabled on debug settings


* Reg 2: HARDWARE_DEBUG_NUMBER 

Write this register to output a number to the pc console. Must be enabled on debug settings


* Reg 3-255: Unused
