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Chapter 6 Audio Subsystem
Compaq Deskpro EN Series of Personal Computers
Desktop and Minitower Form Factors
Third Edition - September 1998
6-10
The Extended Mode registers are listed in Table 6-4. Like the compatibility registers listed
previously, 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. Extended mode offers better performance by
providing more precise (higher bit resolution) control of audio levels and more control of audio
processing.
Table 6–4. Extended Mode Audio Mixer Control Register Mapping
Table 6-4.
Extended Mode Audio Mixer Control Register Mapping
Index Function Index Function
14h Voice Volume 60, 62h Master Volume (Left, Right)
1Ah Mic Volume 64h Master Volume Control
1Ch ADC (recording) Source 66h Volume Int. Req. Clear
1Eh Stereo/Mono Switch 74h DMA Transfer( 2
nd
) Count Reload (Low)
32h Master Volume 76h DMA Transfer (2
nd
) Count Reload (Hi)
36h FM Volume 78h 2
nd
DMA Control 1
38h CD Volume 7Ah 2
nd
DMA Control 2
3Eh Line Volume 7Eh Test Register
NOTE: Refer to OEM’s ES1869 data sheet for detailed registers descriptions.
6.3.2.2
FM Synthesis Control
The FM synthesis logic is typically mapped at 388h-38Bh. A total of 243 registers in two banks
are available. Accessing the registers is accomplished by first writing the index to register 388h
(for bank 0) or 38Ah (for bank 1) followed by writing the data to either 389h or 38Bh (for bank 0
or bank 1 respectively). If a succeeding data byte is destined for the same location then the
address need not be re-written. Location 388h can be read for FM synthesizer status. Table 6-5
lists the FM synthsizer control registers.
Table 6–5. FM Synthesizer Control Register Mapping
Table 6-5.
FM Synthesizer Control Register Mapping
Index Bank 0 Function Bank 1 Function
01h Test - all 0s Test - all 0s
02h Timer 1 Not Used
03h Timer 2 Not Used
04h Timer Mask/Timer Start 4-Operator Configure
05h Not Used 4-Operator Enable
08h Key Scale (KSR) # Determiner Not Used
20-35h AM, Vib, EG Type, KSR, Mult. Same as bank 0
40-55h Key Scale Level, Tone Level Same as bank 0
60-75h Attack Rate, Decay Rate Same as bank 0
80-95h Sustain Level, Release Rate Same as bank 0
A0-A8h Frequency Number Same as bank 0
B0-B8h Key On, Block Octave, Frequency No. Same as bank 0
BDh Depth of Block Octave, Frequency No. Not Used
C0-C8h Stereo Left/Right, Feedback, Connection Same as bank 0
E0-F5h Wave Select Same as bank 0
NOTE: Refer to OEM’s ES1869 data sheet for detailed registers descriptions.
Abbreviations:
AM Amplitude Modulation (tremolo)
Vib Vibrato