Machine Type Register
|Short Description||Identifies timing and machine type.|
A write to this register disables the bootrom in config mode
A write with bit 7 set will be accepted in any mode to change only display timing (bits 6-4).
|7||(W) 1 to allow changes to bits 6:4|
|7||(R) Next write to Enhanced ULA Palette Extension ($44) will affect colour byte: 0 = RRRGGGBB, 1 = p000000B|
|6-4||Display timing (affects I/O port decoding (since core 3.1.1)):
|3||1 to toggle user lock on display timing (hard reset = 0) (since core 3.1.0)|
|2-0||Machine type (determines roms loaded and multiface type (since core 3.1.1)):
Core 3.1.1 change: port-decoding now depends on the selected display-mode, not machine-type. So while machine is still in Next type, by changing to 128 display the port decoding does change too (for example $7FFD port is decoded differently on ZX128 vs ZX128+3 machines).