GIME PALETTE
The Color Computer 3 video chip, known as the GIME supports display of up to 16 simultaneous colors out of a palette of 64, much like the EGA graphics adapter for IBM PC-compatibles.
PROGRAMMING
Super Extended BASIC has the following commands:
- PALETTE CMP
- Sets all 16 palette slots to Super Extended BASIC's list of Composite default values
- PALETTE RGB
- Sets all 16 palette slots to Super Extended BASIC's list of RGB default values
- PALETTE palette register, color code
- Sets palette register 0-15 to color code 0-63
The 16 active palette entries are programmed through GIME memory-mapped registers $FFB0 to $FFBF
DEFAULT PALETTES
BOOT
On boot, all palette registers are initialized to Green ($12) by code in $C006 - $C011.
Next, the following values are loaded into the CoCo 3 Palette Registers from PALIMAGE ($C236 - $C245) by code in $C04E - $C05F, after the boot code is moved down to $4xxx.
This color map defaults to Composite colors for use with televisions or monitors connected through RF Out or Composite Out.
PALETTE COLOR SETS
The boot palette colors are duplicated in memory at IM.CMP ($E654 - E663) which is loaded by the PALETTE CMP command.
The composite color set are again duplicated in memory at IM.PALET ($E678 - $E687) which is used as the “current palette” set by the PALETTE <palette register 0-15>, <color code 0-63> command.
For RGB or PAL, the colors are loaded by the PALETTE RGB command from IM.RGB ($E664 - $E673) table.
For CoCo compatibility, the RGB color set should be loaded on initialization for PAL version.
| Register | Color Name | Composite Palette Code | RGB/PAL Palette Code |
|---|---|---|---|
| $FFB0 | Green | $12 | $12 |
| $FFB1 | Yellow | $24 | $36 |
| $FFB2 | Blue | $0B | $09 |
| $FFB3 | Red | $07 | $24 |
| $FFB4 | Buff | $3F | $3F |
| $FFB5 | Cyan | $1F | $10 |
| $FFB6 | Magenta | $09 | $2D |
| $FFB7 | Orange | $26 | $26 |
| $FFB8 | Black | $00 | $00 |
| $FFB9 | Green | $12 | $12 |
| $FFBA | Black | $00 | $00 |
| $FFBB | Buff | $3F | $3F |
| $FFBC | Black | $00 | $00 |
| $FFBD | Green | $12 | $12 |
| $FFBE | Black | $00 | $00 |
| $FFBF | Orange | $26 | $26 |
PALETTES BY MODE
| VDG Alphanumeric | Palette Registers Used | Palette Register Address |
|---|---|---|
| 32 x 16 Background | 13 | $FFBD |
| 32 x 16 Foreground | 12 | $FFBC |
| VDG Semigraphics | Palette Registers Used | Palette Register Address |
|---|---|---|
| SG4 |  | |
| SG6, CSS=0 | | |
| SG6, CSS=1 | | |
| SG8 | | |
| SG12 | | |
| SG24 | | |
| VDG Graphics | Palette Registers Used | Palette Register Address |
|---|---|---|
| CG1, CSS=0 | 0-3 | $FFB0 - $FFB3 |
| CG1, CSS=1 | 4-7 | $FFB4 - $FFB7 |
| RG1, CSS=0 | 8,9 | $FFB8, $FFB9 |
| RG1, CSS=1 | 10,11 | $FFBA, $FFBB |
| CG2, CSS=0 | 0-3 | $FFB0 - $FFB3 |
| CG2, CSS=1 | 4-7 | $FFB4 - $FFB7 |
| RG2, CSS=0 | 8,9 | $FFB8, $FFB9 |
| RG2, CSS=1 | 10,11 | $FFBA, $FFBB |
| CG3, CSS=0 | 0-3 | $FFB0 - $FFB3 |
| CG3, CSS=1 | 4-7 | $FFB4 - $FFB7 |
| RG3, CSS=0 | 8,9 | $FFB8, $FFB9 |
| RG3, CSS=1 | 10,11 | $FFBA, $FFBB |
| CG6, CSS=0 | 0-3 | $FFB0 - $FFB3 |
| CG6, CSS=1 | 4-7 | $FFB4 - $FFB7 |
| RG6, CSS=0 | 8,9 | $FFB8, $FFB9 |
| RG6, CSS=1 | 10,11 | $FFBA, $FFBB |
| GIME Alphanumeric | Palette Registers Used | Palette Register Address |
|---|---|---|
| 32, 40, 64, 80 Background | 0-7 | $FFB0 - $FFB7 |
| 32, 40, 64, 80 Foreground | 8-15 | $FFB8 - $FFBF |
| GIME Graphics | Palette Registers Used | Palette Register Address |
|---|---|---|
| 2-Color | 0 - 1 | $FFB0 - $FFB1 |
| 4-Color | 0 - 3 | $FFB0 - $FFB3 |
| 16-Color | 0 - 15 | $FFB0 - $FFBF |
VIDEO
REFERENCES
Sockmaster's GIME Register Reference
MAME GIME Source - Composite Palettes as hex codes
CoCo 3 Australia Color Palette - Palettes compared
SEE ALSO
Color Computer 3 Service Manual
CoCo3 Secrets Revealed by Microcom Software, 1986
Assembly Language Programming for the CoCo3 by Lawrence Tepolt, 1987
Super Extended BASIC Unravelled by Spectral Associates/Walter Zydhek, 1999
RTS
Return to Tandy Color Computer or Super Extended BASIC