Pin Number Function
FX806A
J/LG/LS
13
Mic Out:
The output of the microphone Op-Amp, used with the Mic In (–) input to provide the required
gain/attenuation using external components as shown in Figure 2. The external components shown are
to assist in the use of this amplifier with either inverting or non-inverting inputs. During Powersave
(Volume Command) this output is placed at V
SS
.
14
Processed Audio In:
The input to the device from such external audio processes as Voice Store and
Retrieve or Frequency Domain Scrambling. This input, which requires to be a.c. coupled with a
capacitor, C
13
, is selected by a Mode Command bit.
15
External Audio Process:
The buffered output of the Input Processing stage. For further external
audio processing prior to re-introduction at the Processed Audio In pin.
16
CALibration Input:
A unique input, intended to be used for dynamic balancing of the modulator drives
and for measuring Deviation Limiter levels. A CUE (beep) input from the FX803 Audio Tone Processor
can be entered on this line. This input is selected via a Mode Command bit (11
H
) and is self-biased.
17
Main Process Out:
The output of the Main Process stage. This output is summed with additional
system inputs as required (Audio, Sub-Audio Signalling, FFSK – See System Overview) in the on-chip
Modulation Summing Amplifier. External components as shown in Figure 2 should be used as required.
18
19
Sum In:
The input and output terminals of the on-chip Modulation Summing Amplifier. External components
are required for input signals, with gain/attenuation setting as shown in Figure 2. For single-signal,
no-gain requirements, Main Process Out may be linked directly to Modulation In.
Sum Out:
20
Modulation In:
The final, composite modulating signal to VCO (Mod 1) and Reference (Mod 2) Output
Drives.
21
Audio Output:
The processed audio signal output intended as a received audio (volume) output.
Though normally used in the Rx mode, operation in Tx is permitted. The output level of this attenuator is
controlled via a Volume Set command. During Powersave this output is placed at V
SS
.
22
Modulation 1 Drive:
The drive to the radio modulator Voltage Controlled Oscillator (VCO), from the
composite audio summing stage.
23
Modulation 2 Drive:
The drive to the radio modulator Reference Oscillator, from the composite audio
summing stage.
NOTE:
These VCO output attenuators are individually adjustable using the Modulator Levels command.
During Powersave these outputs are placed at V
SS
.
24
V
DD
:
Positive supply rail. A single, stable +5 volt supply is required. Levels and voltages within the
Audio Processor are dependant upon this supply.
3
CMLMICRO [ CML MICROCIRCUITS ]
