humblehacker / coco_roms

TRS-80 Color Computer ROM source code

Custom Tandy Color Computer 3 ROM source code

Originally forked from tomctomc/coco_roms, all non-coco3 code has been stripped and the sources modified to be compatible with LWASM.

This repo is more of an 8-bit assembly playground for me. I doubt these mods will be generally useful, but feel free to give it a try if you're interested. I've tried to keep existing code intact as much as possible to hopefully avoid breaking compatibility with other software that mucks around in the standard ROMs, but I make no guarantees.

Modifications so far:

• Custom keymaps
• Functioning control key

Custom keymaps!

You can switch between QWERTY and Dvorak by poking a 0 (QWERTY) or a 2 (DVORAK) to address 0xA201. For example:

POKE &HA201,2 ' switch to Dvorak
POKE &HA201,0 ' switch to QWERTY

Keyboard matrix

Each key is assigned an index based on its position in the keyboard matrix:

index = 8 × row + column

	PB0	PB1	PB2	PB3	PB4	PB5	PB6	PB7
PA0	@	A	B	C	D	E	F	G
PA1	H	I	J	K	L	M	N	O
PA2	P	Q	R	S	T	U	V	W
PA3	X	Y	Z	↑	↓	←	→	␣
PA4	0	1	2	3	4	5	6	7
PA5	8	9	:	;	,	-	.	/
PA6	ENT	CLR	BRK	ALT	CTL	F1	F2	SHF
PA7	---	---	---	---	---	---	---	---

The keymaps

Here's the keyboard with each key labeled with its index:

And here are the two default keyboard layouts:

1. QWERTY

2. Dvorak

Finally, here's the complete keymap:

			QWERTY				Dvorak
key	index	hex	base	shf	base	shift	base	shf	base	shift
@	0	0x00	@	DC3	0x40	0x13	@	DC3	0x40	0x13
A	1	0x01	A	a	0x41	0x61	A	a	0x41	0x61
B	2	0x02	B	b	0x42	0x62	X	x	0x58	0x78
C	3	0x03	C	c	0x43	0x63	J	j	0x4A	0x6A
D	4	0x04	D	d	0x44	0x64	E	e	0x45	0x65
E	5	0x05	E	e	0x45	0x65	.	>	0x2E	0x3E
F	6	0x06	F	f	0x46	0x66	U	u	0x55	0x75
G	7	0x07	G	g	0x47	0x67	I	i	0x49	0x69
H	8	0x08	H	h	0x48	0x68	D	d	0x44	0x64
I	9	0x09	I	i	0x49	0x69	C	c	0x43	0x63
J	10	0x0A	J	j	0x4A	0x6A	H	h	0x48	0x68
K	11	0x0B	K	k	0x4B	0x6B	T	t	0x54	0x74
L	12	0x0C	L	l	0x4C	0x6C	N	n	0x4E	0x6E
M	13	0x0D	M	m	0x4D	0x6D	M	m	0x4D	0x6D
N	14	0x0E	N	n	0x4E	0x6E	B	b	0x42	0x62
O	15	0x0F	O	o	0x4F	0x6F	R	r	0x52	0x72
P	16	0x10	P	p	0x50	0x70	L	l	0x4C	0x6C
Q	17	0x11	Q	q	0x51	0x71	/	?	0x2F	0x3F
R	18	0x12	R	r	0x52	0x72	P	p	0x50	0x70
S	19	0x13	S	s	0x53	0x73	O	o	0x4F	0x6F
T	20	0x14	T	t	0x54	0x74	Y	y	0x59	0x79
U	21	0x15	U	u	0x55	0x75	G	g	0x47	0x67
V	22	0x16	V	v	0x56	0x76	K	k	0x4B	0x6B
W	23	0x17	W	w	0x57	0x77	,	<	0x2C	0x3C
X	24	0x18	X	x	0x58	0x78	Q	q	0x51	0x71
Y	25	0x19	Y	y	0x59	0x79	F	f	0x46	0x66
Z	26	0x1A	Z	z	0x5A	0x7A	;	+	0x3B	0x2B
↑	27	0x1B	↑	↑	0x5E	0x5F	↑	↑	0x5E	0x5F
↓	28	0x1C	↓	↓	0x0A	0x5B	↓	↓	0x0A	0x5B
←	29	0x1D	←	←	0x08	0x15	←	←	0x08	0x15
→	30	0x1E	→	→	0x09	0x5D	→	→	0x09	0x5D
␣	31	0x1F	␣	␣	0x20	0x20	␣	␣	0x20	0x20
0	32	0x20	0	DC2	0x30	0x12	0	DC2	0x30	0x12
1	33	0x21	1	!	0x31	0x21	1	!	0x31	0x21
2	34	0x22	2	"	0x32	0x22	2	"	0x32	0x22
3	35	0x23	3	#	0x33	0x23	3	#	0x33	0x23
4	36	0x24	4	$	0x34	0x24	4	$	0x34	0x24
5	37	0x25	5	%	0x35	0x25	5	%	0x35	0x25
6	38	0x26	6	&	0x36	0x26	6	&	0x36	0x26
7	39	0x27	7	'	0x37	0x27	7	'	0x37	0x27
8	40	0x28	8	(	0x38	0x28	8	(	0x38	0x28
9	41	0x29	9	)	0x39	0x29	9	)	0x39	0x29
:	42	0x2A	:	*	0x3A	0x2A	:	*	0x3A	0x2A
;	43	0x2B	;	+	0x3B	0x2B	S	s	0x53	0x73
,	44	0x2C	,	<	0x2C	0x3C	W	w	0x57	0x77
-	45	0x2D	-	=	0x2D	0x3D	-	=	0x2D	0x3D
.	46	0x2E	.	>	0x2E	0x3E	V	v	0x56	0x76
/	47	0x2F	/	?	0x2F	0x3F	Z	z	0x5A	0x7A
ENT	48	0x30	CR	CR	0x0D	0x0D	CR	CR	0x0D	0x0D
CLR	49	0x31	FF	\	0x0C	0x5C	FF	\	0x0C	0x5C
BRK	50	0x32	ETX	ESC	0x03	0x1B	ETX	ESC	0x03	0x1B
ALT	51	0x33	NUL	NUL	0x00	0x00	NUL	NUL	0x00	0x00
CTL	52	0x34	NUL	NUL	0x00	0x00	NUL	NUL	0x00	0x00
F1	53	0x35	EOT	ACK	0x04	0x06	EOT	ACK	0x04	0x06
F2	54	0x36	ENQ	BEL	0x05	0x07	ENQ	BEL	0x05	0x07

You can also apply any arbitrary keymap from BASIC. See colmak.bas for an example.

Functioning Control Key

By default, the control key in BASIC does nothing. Sure you can read its state by peeking the KEYBUF at $0156, but wouldn't it be nice if you could use it directly?

This mod does just that. It will return to BASIC the appropriate ASCII code when Control is pressed along with any key from @ to Z¹. For example, pressing CTRL-M will return $0D, the same code as pressing ENTER directly.

Footnotes

1. Really any key up to _ (ASCII $5F), but the coco doesn't have any keys past ASCII Z. ↩