Low Voltage CTCSS Encoder/Decoder
5
MX465
Pin No.
15
Signal
RX TONE DETECT
Type
output
Description
In RX mode this output will go to logic 1 during a
successful decode. It must be externally integrated to
control response and deresponse times (see Table 3).
The CTCSS sinewave output appears on this pin under
control of the
RX/ TX
pin. When not transmitting a tone,
TX TONE OUT may be biased to V
DD
/2. (see Table 3).
RX or TX modes selected in Parallel Mode (see Figure
4). In Serial Mode this function is serially loaded. This
pin is internally pulled to V
DD
via a 1M
Ω
resistor.
In RX mode this pin operates as a ‘Push To Listen’
function by enabling the RX audio path, thus overriding
the tone squelch function (Parallel Mode). In Serial Mode
this function is loaded serially. Internal pull-up to V
DD
High pass filtered RX AUDIO OUT. This pin outputs
audio when RX TONE DECODE = logic 0, PTL = logic 1,
or when Notone is programmed (see Table 4). In TX
mode this pin is biased to V
DD
/2.
High pass filtered TX AUDIO OUT pin. In TX mode this
pin outputs audio present at the TX AUDIO IN pin. In RX
mode this pin is biased to V
DD
/2
Output of an internally generated V
DD
/2 bias level that
would normally be externally bypassed to V
SS
via
capacitor C6.
In TX mode TX AUDIO IN may be prefiltered, using the
TX Audio path, thus helping to avoid talk-off due to
intermodulation of speech frequencies with the
transmitted CTCSS tone. Internally biased to V
DD
/2.
Input to the audio high pass filter in RX mode. Internally
biased to V
DD
/2.
Input to the CTCSS tone detector. Internally biased to
V
DD
/2.
16
TX TONE OUT
output
17
RX/ TX
input
18
PTL
input
19
RX AUDIO OUT
output
20
TX AUDIO OUT
output
21
V
BIAS
output
22
TX AUDIO IN
input
23
24
RX AUDIO IN
TONE INPUT
input
input
Table 1: Signal List
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