CML Semiconductor Products
PRODUCT INFORMATION
FX365C
Features
Low-Voltage (3-Volt) Supply
39 Programmable Sub-Audio
Tones + N
OTONE
Meets MPT1306 and EIA - 220 B
High Voiceband/CTCSS Isolation
Separate Sub-Audio and Rx/Tx
Audio Paths and Filtering
Tx
Tx AUDIO
INPUT
Rx AUDIO
INPUT
Rx
XTAL/CLOCK
XTAL
XTAL/CLOCK
GENERATOR
SUB-AUDIO PATH
VOICE-AUDIO PATH
300Hz
Low-Voltage CTCSS Encoder/
Decoder
Publication D/365C/3 October 1995
Applications
Mobile Radio Systems
Community Base Stations
鈥淪ports Radio鈥?(Japan)
Sub-Audio Signalling and Selec-
tive Calling
Status and Alarm Systems
Amateur Radio
Tx
Tx AUDIO
OUTPUT
(Rx)
CONTROL
Rx AUDIO
OUTPUT
V
DD
(Rx)
SUB-AUDIO
TONE INPUT
f
TONE
DIGITAL
PERIOD
DETECTOR
OUTPUT
LATCH
TONE FREQUENCY
BUS
Rx TONE
DETECT
LOAD/LATCH
SERIAL ENABLE 1/D
5
SERIAL ENABLE 2/D
4
SERIAL DATA/D
3
SERIAL CLOCK/D
2
D
1
D
0
Rx/Tx
PTL
V
DD
3
2V
DD
3
V
BIAS
FX365C
8-BIT
SERIAL
SHIFT
REGISTER
8-BIT
LATCH
PROGRAM
LOGIC
TONE
GENERATOR
Tx TONE
OUTPUT
Tx ENABLE
CONTROL
V
SS
LOGIC
DECODE
COMPARATOR REF.
DECODE
COMPARATOR
INPUT
LOGIC
+
-
DECODE COMPARATOR
Rx TONE DECODE
OUTPUT
Fig.1 Functional Block Diagram
Brief Description
The FX365C is a 3-volt, half-duplex predictive
Continuous Tone Controlled Squelch System
(CTCSS) encoder/decoder microcircuit. The FX365C
has integral voice-band filtering for prefiltering of Tx
audio and the rejection of the CTCSS tone in receive.
Under 碌Processor control, the FX365C will encode
and decode any one of 39 sub-audio frequencies
(+N
OTONE
) in the range 67.0Hz to 250.3Hz. Tone
frequencies and all functional commands can be
loaded to the device in either pin-selectable 8-bit
parallel or serial format.
A separate, Rx/Tx voice-audio path is available with
a highpass (sub-audio reject) filter automatically
placed in the relevant Rx or Tx voice line.
The Rx sub-audio (CTCSS) path contains a
(selected tone frequency) bandpass filter and period
detector providing a logic level output (Rx Tone
Detect) to indicate a successful decode operation.
Rx 鈥淧ress to Listen鈥?(PTL) and Tx 鈥淪quelch-Tail
Elimination鈥?functions are available in both command
loading modes. The squelch-tail elimination function
will provide (Tx tone) phase-reversal to minimise the
annoying audio outputs that occur at the receiver on
completion of a transmission.
Tone frequencies and filter accuracies are
maintained by an on-chip 1.0MHz clock oscillator
employing an external crystal or clock pulse input.
The FX365C, which exhibits high audio and sub-
audio performance with low falsing, is available in 24-
pin DIL and small outline SMD packages.
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