Difference between revisions of "Machine Type Register"
From SpecNext official Wiki
(core 3.1.0 changes/refresh) |
(core 3.1.3 changes/refresh) |
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| 7 || (R) Next write to {{NextRegNo|$44}} will affect colour byte: 0 = RRRGGGBB, 1 = p000000B | | 7 || (R) Next write to {{NextRegNo|$44}} will affect colour byte: 0 = RRRGGGBB, 1 = p000000B | ||
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− | | 6-4 || Display timing. %000 | + | | 6-4 || Display timing. %000: internal usage %001: ZX 48k; %010: ZX 128k/+2 (Grey); %011: ZX +2A-B/+3e/Next Native; %100: Pentagon. |
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| 3 || 1 to toggle user lock on display timing (hard reset = 0) (since core 3.1.0) | | 3 || 1 to toggle user lock on display timing (hard reset = 0) (since core 3.1.0) | ||
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Writeable only in config mode, may affect port decoding and enabling of some hardware. | Writeable only in config mode, may affect port decoding and enabling of some hardware. | ||
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+ | |||
+ | 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 (for example $7FFD port is decoded differently on ZX128 vs ZX128+3 machines). |
Revision as of 21:01, 29 March 2020
Number | $03 |
---|---|
Readable | Yes |
Writable | Yes |
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).
Bit | Function |
---|---|
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. %000: internal usage %001: ZX 48k; %010: ZX 128k/+2 (Grey); %011: ZX +2A-B/+3e/Next Native; %100: Pentagon. |
3 | 1 to toggle user lock on display timing (hard reset = 0) (since core 3.1.0) |
2-0 | Machine type:
%000: Config mode; %001: ZX 48k; %010: ZX 128k/+2 (Grey); %011: ZX +2A-B/+3e/Next Native; %100: Pentagon. Writeable only in config mode, may affect port decoding and enabling of some hardware. |
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 (for example $7FFD port is decoded differently on ZX128 vs ZX128+3 machines).