Tandy 1000 SL Technical Reference Manual page 565

Software
Busy:
AX
=
OOC4H
CF
=
1
Input Sound
Inputs sound from the microphone.
Entry Conditions
AH
=
82H
ES:BX
=
buffer address
C X
=
buffer length
DX
Exit Conditions
Not Busy:
AH
=
0
CF
=
0
Busy:
AH
=
0
CF
=
1
=
transfer rate (1-4095, where 1 is the fastest
transfer rate)
4 4 .