Control; Table 6-2. Audio Subsystem; Table 6-3. Compatibility Mode - Compaq EN Series Technical Reference Manual

6.3.2

CONTROL

The audio subsystem is controlled through I/O mapped registers listed in Table 6-2.
Table 6–2. Audio Subsystem I/O Map
I/O
Address Function
201h Joystick
2n0-2n3 FM Synthesizer Address/Data [1]
2n4h Mixer Address
2n5h Mixer Data
2n6h (Read) Activity/Power Status
2n6h (Write) Reset Control
2n7h Power Management
2n8, 2n9h FM Synthesizer Address/Data [2]
NOTES:
n = 2 for primary address (default), = 4 for secondary address.
[1] 20-voice operation
[2] 11-voice operation
Not supported
6.3.2.1 PCM Control
The audio subsystem can operate in either Sound Blaster-compatible mode (the default) or in
extended capability mode.
Table 6-3 lists the audio mixer control registers used by software written for Sound Blaster and
other common audio peripherals. These registers are accessed by writing the index value to I/O
port 2n4h and reading the value from or writing the value to I/O port 2n5h.
Table 6–3. Compatibility Mode Audio Mixer Control Register Mapping
Index Function
00h Mixer Reset
04h Voice Volume
0Ah Mic Volume
0Ch ADC Recording Source [1]
0Eh Stereo/Mono Switch [1]
NOTE: Refer to OEM's ES1869 data sheet for detailed register descriptions.
[1] The filter functions used in Sound Blaster subsystems are not used in the audio subsystem.
Audio Subsystem I/O Map
Compatibility Mode Audio Mixer Control Register Mapping
Compaq Deskpro EN Series of Personal Computers
Third Edition–- September1998
Table 6-2.
I/O
Address Function
2nAh Read Buffer Input Data
2nCh (Read) Status
2nCh (Write) Command/Data
2nEh Data Available Status
2nFh FIFO I/O Address (Extended Mode)
3n0, 3n1h MPU-401 Port
388-38Bh FM Synthesizer (alias of 2n0-2n3h)
-- --
Table 6-3.
Index Function
22h Master Volume
26h FM Volume
28h CD Volume
2Eh Line Volume
-- --
Desktop and Minitower Form Factors
Technical Reference Guide
6-9