Some Programming aids…

To calculate T1CH & T1CL values for an audio frequency tone generator (akin to the DM41X Ladybug version DM41X Progs)

The required count is calculated from Φ2 and the audio frequency required.

Count (decimal)

{ Φ₂ / ( 2 x F ) } - 2

for 1000Hz and a 1MHz Φ₂ :

Count = { 1,000,000 / ( 2 X 1000 ) } - 2 = 498

498d → $01F2

Start in DEC mode (and UNSIGNED integers)

put required audio tone frequency in X

GSBA

Result is shown in hex

e.g.

DEC 1000 GSBA Result 001F2 H

$01F2

T1CH = $01
T1CL = $F2

The Program Listing

43,22,A   | g LBL A
44 0      | STO 0
2         | 20
0
42 44     | f WSIZE (i.e. WSIZE = 20)
1         | 1000000
0
0
0
0
0
0
45 0      | RCL 0
2         | 2
20        | x
10        | /
2         | 2
30        | -
23        | HEX
43 21     | g RTN

To calculate VIA T1 values with different CPU Φ₂ clock frequencies.

Switch to DEC mode. Set word size to 24.

Put required CPU Φ₂ in Y and required audio freq. in X

GSBB

Answer is in HEX.

e.g 1MHz CPU Φ₂ and 1000Hz Audio

1000000 Enter 1000 GSBB

0001F2 H

Timer values T1CL → $F2 and T1CH → $01

or for 4MHz and 100Hz (e.g. for a 10ms TICK)

4000000 Enter 100 GSBB

4E1E H

Timer values T1CL → $1E and T1CH → $4E

• Routine B

42,22, B
44 0
34
44 1
2
4
42 44
45 1
45 0
2
20
10
2
30
23
43 21

— John Pumford-Green 07/08/22 07:14

— John Pumford-Green 24/04/23 16:06