New register system:

243B - Set register #
253B - Set/read value


Register:
(R)		00 => Machine ID
hardware numbers
1 = DE-1 (old)
2 = DE-2 (old)
3 = DE-2 (new)
4 = DE-1 (new)
5 = FBLabs
6 = VTrucco
7 = ZX Spectrum Next
8 = Emulators

(R)		01 => Version (Nibble most significant = Major, Nibble less significant = Minor)
Igual a la segunda puerta de lectura 24D5 en el antiguo sistema, debe volver "0x16" para la versión 1.6.

(R/W)	02 => Reset:
			bits 7-3 = Reserved, must be 0
			bit 2 = (R) Power-on reset
			bit 1 = (R/W) if 1 Hard Reset
			bit 0 = (R/W) if 1 Soft Reset
(W)		03 => Set machine type, only in bootrom or config mode:
			A write in this register disables the bootrom mode (0000 to 3FFF are mapped to the RAM instead of the internal ROM)
			bits 7-5 = Reserved, must be 0
			bits 4-3 = Timing:
				00,
				01 = ZX 48K
				10 = ZX 128K
				11 = ZX +2/+3e
			bit 2 = Reserved, must be 0
			bits 1-0 = Machine type:
				00 = Config mode (bootrom)
				01 = ZX 48K
				10 = ZX 128K
				11 = ZX +2/+3e
(W)		04 => Set page RAM, only in config mode (no bootrom):
			bits 7-5 = Reserved, must be 0
			bits 4-0 = RAM page mapped in 0000-3FFF (32 pages of 16K = 512K)
(R/W)	05 => Peripheral 1 setting, only in bootrom or config mode:
			bits 7-6 = (W) joystick 1 mode (00 = Sinclair, 01 = Kempston, 10 = Cursor)
			bits 5-4 = (W) joystick 2 mode (same as joy1)
			bit 3 = (W) Enable ULAplus (1 = enabled)
			bit 2 = (R/W) 50/60 Hz mode (0 = 50Hz, 1 = 60Hz)
			bit 1 = (R/W) Enable Scanlines (1 = enabled)
			bit 0 = (R/W) Enable Scandoubler (1 = enabled)
(W)		06 => Peripheral 2 setting, only in bootrom or config mode:
			bit 7 = Enable turbo mode (0 = disabled, 1 = enabled)
			bit 6 = DAC chip mode (0 = I2S, 1 = JAP)
			bit 5 = Enable Lightpen  (1 = enabled)
			bit 4 = Enable DivMMC (1 = enabled)
			bit 3 = Enable Multiface (1 = enabled)
			bit 2 = PS/2 mode (0 = keyboard, 1 = mouse)
			bits 1-0 = Audio chip mode (0- = disabled, 10 = YM, 11 = AY)
(R/W)	07 => Turbo mode
			bit 0 = Turbo (0 = 3.5MHz, 1 = 7MHz)

(W)		FF => Debug LEDs (DE-1 and DE-2 only)
