82
Programmable I/O Lines
TM8000 3DK Hardware Developer’s Kit
Application Manual
September 2003
© Tait Electronics Ltd
Audio Paths
shows a simplified block diagram of the receive and transmit
audio paths, the locations of the tap points available, and the tap types.
Audio
Configuration
The audio configuration consists of the following elements:
■
audio source associated with each PTT (CH_MIC_AUD,
AUX_MIC_AUD, AUD_TAP_IN)
■
Rx/PTT type (Rx, Mic PTT, EPTT1, EPTT2)
■
tap out point (R1, R2, R4, R5, R7, R10, T3, T4)
■
tap out type (C-Bypass Out, D-Split, E-Splice)
■
tap out unmute condition
■
tap in point (T3, T4, T5, T8, T12, T13, R7, R10)
■
tap in type (A -Bypass In, B-Combine, E-Splice)
■
tap in unmute condition
Audio Source
For each PTT (Mic PTT, EPTT1 and EPTT2) a different audio source can
be selected. These audio sources are CH_MIC_AUD, AUX_MIC_AUD
and AUD_TAP_IN.
Note
You can allocate an audio tap input at the same time as a micro-
phone input by setting the audio source for a PTT to
CH_MIC_AUD or AUX_MIC_AUD, and defining a tap in and
out point for the same PTT. However, audio samples from the
audio tap input will overwrite those from the microphone input,
unless the tap in type and tap out type are set to ‘Splice’.
Figure 3.14
Receive and transmit audio paths - simplified block diagram
receiver
deviation
demodulator
output
300Hz
de-
future
processing
option
normaliser
3kHz
LPF
HPF
emphasis
audio to
volume
control
audible
indicators
R10
R7
R5
R4
R2
R1
audio to
dev.
transmitter
modulator
pre-
future
processing
option
scaler
limiter and
3kHz LPF
emphasis
ALC
mic
audio
T3
T5
T8
T12
T13
300Hz
HPF
future
processing
option
T4
Key:
tap point (tap in or tap out)
LPF
low-pass filter
HPF high-pass filter
ALC auto level controlled
+
receive audio path
transmit audio path
and speaker
+
type A
type B
type C
type D
type E
tap types:
Combine
Bypass Out
Split
Splice
Bypass In