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BBC Micro Elite

Screen mode: TVT1

Name: TVT1 [View in context] Type: Variable Category: Screen mode Summary: Palette data for space and the two dashboard colour schemes
Palette bytes for use with the split-screen mode (see IRQ1 below for more details). Palette data is given as a set of bytes, with each byte mapping a logical colour to a physical one. In each byte, the logical colour is given in bits 4-7 and the physical colour in bits 0-3. See p.379 of the Advanced User Guide for details of how palette mapping works, as in modes 4 and 5 we have to do multiple palette commands to change the colours correctly, and the physical colour value is EOR'd with 7, just to make things even more confusing. Similarly, the palette at TVT1+16 is for the monochrome space view, where logical colour 1 is mapped to physical colour 0 EOR 7 = 7 (white), and logical colour 0 is mapped to physical colour 7 EOR 7 = 0 (black). Each of these mappings requires six calls to SHEILA+&21 - see p.379 of the Advanced User Guide for an explanation. The mode 5 palette table has two blocks which overlap. The block used depends on whether or not we have an escape pod fitted. The block at TVT1 is used for the standard dashboard colours, while TVT1+8 is used for the dashboard when an escape pod is fitted. The colours are as follows: Normal (TVT1) Escape pod (TVT1+8) Colour 0 Black Black Colour 1 Red Red Colour 2 Yellow White Colour 3 Green Cyan
.TVT1 EQUB &D4, &C4 \ This block of palette data is used to create two EQUB &94, &84 \ palettes used in three different places, all of them EQUB &F5, &E5 \ redefining four colours in mode 5: EQUB &B5, &A5 \ \ 12 bytes from TVT1 (i.e. the first 6 rows): applied EQUB &76, &66 \ when the T1 timer runs down at the switch from the EQUB &36, &26 \ space view to the dashboard, so this is the standard \ dashboard palette EQUB &E1, &F1 \ EQUB &B1, &A1 \ 8 bytes from TVT1+8 (i.e. the last 4 rows): applied \ when the T1 timer runs down at the switch from the \ space view to the dashboard, and we have an escape \ pod fitted, so this is the escape pod dashboard \ palette \ \ 8 bytes from TVT1+8 (i.e. the last 4 rows): applied \ at vertical sync in LINSCN when HFX is non-zero, to \ create the hyperspace effect in LINSCN (where the \ whole screen is switched to mode 5 at vertical sync) EQUB &F0, &E0 \ 12 bytes of palette data at TVT1+16, used to set the EQUB &B0, &A0 \ mode 4 palette in LINSCN when we hit vertical sync, EQUB &D0, &C0 \ so the palette is set to monochrome when we start to EQUB &90, &80 \ draw the first row of the screen EQUB &77, &67 EQUB &37, &27