6809 Assembly programming for the TRS-80 CoCo 3

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

	Tandy CoCo 3 (TRS-80 Color Computer 3)
Cpu	1.8 mhz 6809/6309
Ram	128kk
Max Resolution	Up to 320x200 @ 16 color

ChibiAkumas Dragon/CoCo Tutorials

Lesson P1 - Keyboard and Joystick reading on the Dragon / CoCo [DGN]

Lesson P4 - Bitmap Drawing on the Dragon / Tandy CoCo [DGN]

Lesson P8 - Sound on the Dragon / Tandy CoCo [DGN]

Lesson P9 - 16 color Bitmap Drawing on the TRS-80 CoCo 3 [CCO]

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