INT 1Ah, 80h (128) Set Up Sound Multiplexer PCjr
Determines the source to be used for sound generation.
On entry: AH 80h
AL Sound source
00h - 8253 channel 2
01h - Cassette input
02h - "Audio in" line on I/O channel
03h - Complex sound generator chip
(TI 76496)
Returns: CF Set if error; else cleared
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Notes: This service is available only for the PCjr. ATs,
XT-286s, and PC Convertibles will set the Carry
Flag, thus reporting an error state. Previous
machines will report unpredictable results
(including the state of the Carry Flag).
On power-up, the default sound source is the 8253
programmable-timer chip, via channel 2.