To select a column of the Keymap we use CRU Address 0024h, we can then read in from the address 0006h

We can read a whole column into R4 with ST R4,8

We can test a single bit with TB n - where n is the bit (offset from 0006h) to test 

CRU Address	Col 0	Col 1	Col 2	Col 3	Col 4	Col 5	Col 6	Col 7
0006h	=	.	,	M	N	/	J1-Fire	J2-Fire
0008h	space	L	K	J	H	;	J1-Right	J2-Right
000Ah	enter	O	I	U	Y	P	J1-Left	J2-Left
000Ch		9	8	7	6	0	J1-Down	J2-Down
000Eh	fctn	2	3	4	5	1	J1-Up	J2-Up
0010h	shift	S	D	F	G	A
0012h	ctrl	W	E	R	T	Q
0014h		X	C	V	B	Z

Sound on the TI99

The TMS9919 uses memory mapped port 8400h for its sound control... This port takes a single byte of data - except for tones which take 2 bytes

The data we send is in the format below:

		Bits
Command	Bit Details	7	6	5	4	3	2	1	0
Format Template	L=Latch C=Channel T=Type XXXX=Data	L	C	C	T	D	D	D	D
Tone - Command 1/2	C=Channel L=tone Low data	1	C	C	0	L	L	L	L
Tone - Command 2/2	H= High tone data (Higher numbers = lower tone)	0	-	H	H	H	H	H	H
Volume	C=Channel (0-2)  V=Volume (15=silent 0=max)	1	C	C	1	V	V	V	V
Noise Channel	(Channel 3)  M=Noise mode (1=white) R=Rate (3=use tone 2)	1	1	1	0	-	M	R	R