Audio volume register channel 0
AUDV0 = $19
Audio Volume Channel 0
| WRITE | Name | D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0
|
| $19 | AUDV0 | D3 | D2 | D1 | D0 |
Registers AUDV0 and AUDV1 control the audio volume registers which set the pull down impedance driving the audio output pads.
Volume
Volume is controlled by writing to a 4 bit audio volume register (AUDV0, AUDV1). Writing 0 to these registers turns sound off completely, and writing any value up to 15 increases the volume accordingly.
D3 | D2 | D1 | D0 | Audio Output pull down current | |||||
0 | 0 | 0 | 0 | No output current | |||||
0 | 0 | 0 | 1 | lowest | |||||
...
| |||||||||
1 | 1 | 1 | 0 | ||||||
1 | 1 | 1 | 1 | highest | |||||
SECAM Compatibility
SECAM machines use PAL software with one exception. when a sound is to be turned off, it must be one by setting AUDV0/AUDV1 to 0, not by setting AUDC0/AUDC1 to 0. Otherwise, you get an obnoxious background sound.
Related
Related
see TIA