MODE 9

MODE 9 is the unofficial title of an ultra-low resolution screen MODE, developed by Ian Robertson and published in The Micro User magazine (November 1985, p.123). It works on the BBC Micro but not the Electron or Master, or the Archimedes (where MODE 9 is officially a 16-colour version of MODE 1).

The MODE 9 code adapts the MODE 6 screen to provide a 10 × 25 text display in 16 colours. The MOS does not allow complete support of this MODE and some bugs can be seen: for instance, text windows do not work correctly.

'MODE 9'

Type	Bitmapped, text only ('ASCII')
Resolution	Text	10 × 25 characters
	Graphics	n/a
Character size	8 × 10 pixels, top 8 lines user definable
Pixel aspect	4:1 (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	8192 bytes
	on screen	8000 bytes
Address range	Model B etc.	&6000..&7FFF
Configuration	Video ULA control register	&80
	Video ULA palette register file	&07 &16 &25 &34 &43 &52 &61 &70 &8F &9E &AD &BC &CB &DA &E9 &F8
	CRTC register file	&3F &28 &31 &24 &1E &02 &19 &1B &01 &09 &67 &09 (from table in MOS 1.20 at &C492..&C49D)

MODE 9 is also the unofficial title of a medium-resolution screen MODE, selectable with the *MODE command or the NewModes sideways ROM module.

The MODE 9 code adapts the MODE 2 screen to provide a 4-colour version of MODE 1, 40 × 32 characters in 4 colours. It does this by redefining the character set to provide thin characters.

'MODE 9'

Type	Bitmapped
Resolution	Text	40 × 32 characters
	Graphics	160 × 256
Character size	4 × 8 pixels
Pixel aspect	2:1 (wide)
Bits per pixel	2
Default palette	Logical colour	Actual colour
	0	0 (black)
	1	1 (red)
	2	3 (yellow)
	3	7 (white)
Memory	allocated	20480 bytes
	on screen	20480 bytes
Address range	Model B etc.	&3000..&7FFF
Configuration	Video ULA control register	&D4
	Video ULA palette register file	&07 &17 &26 &36 &47 &57 &66 &76 &84 &94 &A0 &B0 &C4 &D4 &E0 &F0
	CRTC register file	&3F &28 &31 &24 &26 &00 &20 &22 &01 &07 &67 &08

MODE 9 can be created manually with the following code running in the I/O processor.

   BASIC:
   MODE 2     :REM Base MODE
   ?&30A=39   :REM Characters per line
   ?&34F=8    :REM Bytes per character
   *FX154,212
   
   6502:
   LDA #22:JSR OSWRCH
   LDA #02:JSR OSWRCH           \ Base MODE
   LDA #&27:STA &30A            \ Characters per line
   LDA #&08:STA &34F            \ Byte per character
   LDA #154:LDX #212:JSR OSBYTE \ Cursor width

The character set needs to be redefined to be four pixels wide, such as with the one used with NewModes.

See Also

• NewModes

References

-- Jgharston (talk) 17:22, 12 October 2016 (UTC) beardo 12:52, 20 September 2006 (BST)