Machine Type Register

Number	$03
Readable	Yes
Writable	Yes
Short Description	Identifies timing and machine type.

Only valid in IPL or config mode (0x0000-0x3FFF are mapped to the RAM instead of the internal ROM).

A write to this register disables the IPL.

A write with bit 7 set will be accepted in any mode to change only timing (bits 6-4).

Bit	Function
7	(W) Lock Timing (change timing in any mode)
7	(R) Next write to Enhanced ULA Palette Extension ($44) will affect colour byte: 0 = RRRGGGBB, 1 = p000000B
6-4	Timing. %000-001: ZX 48k; %010: ZX 128k/+2 (Grey); %011: ZX +2A-B/+3e/Next Native; %100: Pentagon.
3	Reserved, must be 0
2-0	Machine type. %000: Config mode; %001: ZX 48k; %010: ZX 128k/+2 (Grey); %011: ZX +2A-B/+3e/Next Native; %100: Pentagon.