MODE 2
MODE 2 is a low-resolution screen MODE, introduced on the BBC Micro Model B and supported by the entire BBC series including the Archimedes. It allows colour graphics to be shown but leaves only 9 KB for programs -- even less if a disc interface or Econet is fitted.
MODE 2 is the only official MODE to offer 4 bits per pixel. This was usually used to display full colour graphics; several applications (including "Island" and "Planets" from the Acorn Electron Introductory Cassette) used it for cyclic animations by reprogramming the palette several times a second. The MOS makes this convenient by offering extended paint options in GCOL and commands to redefine the palette.
| Type | Graphical ('ASCII') | |
| Resolution | Text | 20 × 32 characters |
| Graphics | 160 × 256 pixels | |
| Character size | 8 × 8 pixels, user definable | |
| Pixel aspect | 2:1 (wide) | |
| Bits per pixel | 4 | |
| Default palette | Logical colour | Actual colour |
|---|---|---|
| 0 | 0 (black) | |
| 1 | 1 (red) | |
| 2 | 2 (green) | |
| 3 | 3 (yellow) | |
| 4 | 4 (blue) | |
| 5 | 5 (magenta) | |
| 6 | 6 (cyan) | |
| 7 | 7 (white) | |
| 8 | 8 (flashing black/white) | |
| 9 | 9 (flashing red/cyan) | |
| 10 | 10 (flashing green/magenta) | |
| 11 | 11 (flashing yellow/blue) | |
| 12 | 12 (flashing blue/yellow) | |
| 13 | 13 (flashing magenta/green) | |
| 14 | 14 (flashing cyan/red) | |
| 15 | 15 (flashing white/black) | |
| Memory | allocated | 20480 bytes |
| on screen | 20480 bytes | |
| Address range | Model B etc. | &3000..&7FFF |
| Configuration | Video ULA control register | &F4 |
| Video ULA palette register file | &07 &16 &25 &34 &43 &52 &61 &70 &8F &9E &AD &BC &CB &DA &E9 &F8 | |
| CRTC register file | &7F &50 &62 &28 &26 &00 &20 &22 &01 &07 &67 &08 (from table in MOS 1.20 at &C46E..&C479) | |
| Screen display MODEs |
|---|
|
MODE 0 | MODE 1 | MODE 2 | MODE 3 | MODE 4 | MODE 5 | MODE 6 | MODE 7 |
-- beardo 14:11, 16 September 2006 (BST)
