Pin Number
Function
DIL
Quad
FX506P FX506LG
FX506LS
1
2
Xtal: The output of the 4.0MHz on-chip clock oscillator.
Xtal/Clock: The input to the on-chip 4.0MHz clock oscillator inverter. All oscillator components are
included on-chip. A 4.0MHz Xtal or externally derived clock should be connected here.
See Figure 2.
3
4
VDD: Positive supply rail. A single, stable +5-volt supply is required. Levels and voltages within the
Audio Processor are dependent upon this supply.
Post Process Audio Input: The analogue input to the Post-Process Path from external audio
operations. Inputs to this pin should be a.c. coupled via a capacitor C7.
See Figures 2 and 4.
5
6
Pre-Process Audio Output: The analogue output to external audio operations.
See Figure 4.
Rx Audio Input: The input from the radio receiver demodulator. This input, which requires to be
a.c. coupled via capacitor C6, is selected by serial data. Audio at this input will be available for use
as a signal-squelch noise source. See Figures 2 and 4.
7
8
VBIAS: The output of the on-chip analogue bias circuitry, held internally at VDD/2. This pin should be
decoupled to VSS via capacitor C1. See Figure 2.
CTCSS/Data Input: To allow the introduction of sub-audio tones or data to the VCO drives.
By manipulation of bits 17, 18 and 19 this input can be “mixed” into the signal path or added as a
burst in between speech segments.
9
Tx Audio Input: The pre-process transmit audio input. This input can be driven from an external
source or from the FX506 Mic. input circuitry. See Figures 2, 3 and 4.
10
Mic. Output: The output of the microphone multiplexer, selected by serial input data. If additional
gain is required for the pre-process input, an external amplifier as shown in Figure 3 is
recommended.
11
Mic.1 Input:
These separate microphone audio inputs are individually selected by the
serial input data. See Figures 2, 3 and 4.
Mic.2 Input:
12
13
VSS: Negative supply rail (GND).
2
CMLMICRO [ CML MICROCIRCUITS ]
