It has been extended with a chip known as the 'GIME... this enhances the CoCo with better graphics and bank switching extra memory
Clever owners of the CoCo even figured out that the Cpu could be swapped with the more advanced 6309
| The CoCo 3 is backwards compatible
with the original CoCo/Dragon It has been extended with a chip known as the 'GIME... this enhances the CoCo with better graphics and bank switching extra memory Clever owners of the CoCo even figured out that the Cpu could be swapped with the more advanced 6309 |
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Extended Memory Map
| Page | 19 bit address | Purpose | Default Logical 16 bit address |
| $00 | $00000 | 512k upgrade | |
| $30 | $60000 | High Res Screen Ram | |
| $34 | $68000 | High Res Buffer | |
| $35 | $6A000 | Secontry Stack | |
| $36 | $6C000 | High Res Text Screen | |
| $37 | $6E000 | Unused | |
| $38 | $70000 | Basic 32k | $0000 |
| $3C | $78000 | Extended Color Basic | $8000 |
| $3D | $7A000 | Color Basic | $A000 |
| $3E | $7C000 | Cartridge | $C000 |
| $3F | $7E000 | Super Extended Basic | $E000 |
| $7FF00 | Dedicated Addresses | $FF00 | |
| $7FFFF | ----------------------------- | $FFFF |
MMU Bank Switching
Bank switching is performed by addresses $FFA0-FFAF
There are two sets of options Task 0 (Executive Set) and Task 1 (Task Set)... which of these is active is selected by bit 0 of $FF91... this allows for quick switching between two options
| $FF91 Bit0=0 | $FF91 Bit0=1 | |||
| Bank | Address Range | Executive Set | Task Set | Default |
| 0 | $0000 | $FFA0 | $FFA8 | $38 |
| 1 | $2000 | $FFA1 | $FFA9 | $39 |
| 2 | $4000 | $FFA2 | $FFAA | $3A |
| 3 | $6000 | $FFA3 | $FFAB | $3B |
| 4 | $8000 | $FFA4 | $FFAC | $3C |
| 5 | $A000 | $FFA5 | $FFAD | $3D |
| 6 | $C000 | $FFA6 | $FFAE | $3E |
| 7 | $E000 | $FFA7 | $FFAF | $3F |
GIME Addresses
| Address | ShortName | Purpose | Bits | Sample | Notes |
| $FF90 | INIT0 | Init Register 0 | CMIFRSr- | C=Coco12 M=Mmu on | |
| $FF91 | INIT1 | Init Register 1 | -MT-----m | m=mmu TASK T=Timer spped M=Memory type | |
| $FF92 | IRQEN | IRQ enable | --THVRKC | C=Cart K=Key R=Rs232 V=Vsync H=Hsync T=Timer | |
| $FF93 | IFRQEN | FIRQ Enable | --THVRKC | C=Cart K=Key R=Rs232 V=Vsync H=Hsync T=Timer | |
| $FF94 | TIMERH | Timer H Byte | ----HHHH | 12 bit Timer | |
| $FF95 | TIMERH | Timer L Byte | LLLLLLLL | 12 bit Timer | |
| $FF96 | Unused | ||||
| $FF97 | Unused | ||||
| $FF98 | VMODE | Video Mode | P-DMFLLL | L=Lines per row / F=Freq (60/50) M=Mono D=Descender P=Planes(Text/Graphics) | |
| $FF99 | VRES | Video Resolution | -LLBBBCC | C=Colors () B=Bytes per row (6=128) L=Lines (0=192) | |
| $FF9A | BCOLOR | Border Color | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FF9B | VBANK | 2MB Upgrade | ------VV | ||
| $FF9C | VSCROLL | Vertical Scroll | ----VVVV | Vertical Smooth SCroll | |
| $FF9D | VOFF_H | Vertical Offset H | $C0 | Screen Ram Address /8.... $C000 =$60000 | |
| $FF9E | VOFF_L | Vertical Offset L | $00 | Screen Ram Address /8.... $C000 =$60000 | |
| $FF9F | HOFF | Horizontal offset | VOOOOOOO | V=Use Virtual screen (256 bytes wide) O=Hoffset | |
| $FFA0 | MMU0_0 | MMU Task 0 $0000-1FFF | ---HHHHH | $38 | |
| $FFA1 | MMU0_1 | MMU Task 0 $2000-3FFF | ---HHHHH | $39 | |
| $FFA2 | MMU0_2 | MMU Task 0 $4000-5FFF | ---HHHHH | $3A | |
| $FFA3 | MMU0_3 | MMU Task 0 $6000-7FFF | ---HHHHH | $3B | |
| $FFA4 | MMU0_4 | MMU Task 0 $8000-9FFF | ---HHHHH | $3C | |
| $FFA5 | MMU0_5 | MMU Task 0 $A000-BFFF | ---HHHHH | $3D | |
| $FFA6 | MMU0_6 | MMU Task 0 $C000-DFFF | ---HHHHH | $3E | |
| $FFA7 | MMU0_7 | MMU Task 0 $E000-FFFF | ---HHHHH | $3F | |
| $FFA8 | MMU1_0 | MMU Task 1 $0000-1FFF | ---HHHHH | $38 | |
| $FFA9 | MMU1_1 | MMU Task 1 $2000-3FFF | ---HHHHH | $39 | |
| $FFAA | MMU1_2 | MMU Task 1 $4000-5FFF | ---HHHHH | $3A | |
| $FFAB | MMU1_3 | MMU Task 1 $6000-7FFF | ---HHHHH | $3B | |
| $FFAC | MMU1_4 | MMU Task 1 $8000-9FFF | ---HHHHH | $3C | |
| $FFAD | MMU1_5 | MMU Task 1 $A000-BFFF | ---HHHHH | $3D | |
| $FFAE | MMU1_6 | MMU Task 1 $C000-DFFF | ---HHHHH | $3E | |
| $FFAF | MMU1_7 | MMU Task 1 $E000-FFFF | ---HHHHH | $3F | |
| $FFB0 | PAL0 | Palette entry 0 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFB1 | PAL1 | Palette entry 1 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFB2 | PAL2 | Palette entry 2 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFB3 | PAL3 | Palette entry 3 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFB4 | PAL4 | Palette entry 4 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFB5 | PAL5 | Palette entry 5 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFB6 | PAL6 | Palette entry 6 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFB7 | PAL7 | Palette entry 7 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFB8 | PAL8 | Palette entry 8 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFB9 | PAL9 | Palette entry 9 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFBA | PAL10 | Palette entry 10 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFBB | PAL11 | Palette entry 11 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFBC | PAL12 | Palette entry 12 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFBD | PAL13 | Palette entry 13 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFBE | PAL14 | Palette entry 14 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits | |
| $FFBF | PAL15 | Palette entry 15 | --RGBRGB | Birt 0-2=low bits bits 3-5 = top bits |