Pin Number
FX375J FX375LG
FX375LH FX375LS
1
2
Function
Xtal/Clock:
The input to the clock oscillator inverter. An external 4MHz Xtal or clock
input is to be applied at this pin. See Figure 2.
2
3
Xtal:
The 4MHz output of the clock oscillator inverter. See Figure 2.
3
4
Load/Latch:
This input regulates the operation of the eight input latches : D
0
, D
1
, D
2
,
D
3
, D
4
, D
5
, Rx/Tx and Private Enable for both parallel and serial input load modes.
Rx/Tx and Private Enable inputs can be used independently in either mode by the use
of Load/Latch and Control inputs configured as shown in Table 3, the data format
(D
0
– D
5
), remains as set. This input has an internal 1MΩ pullup resistor.
4
5
6
7
8
9
–
5
6
7
–
–
D
5
– (Serial Enable 1) :
D
4
– (Serial Enable 2) :
D
3
– (Serial Data Input) :
D
2
– (Serial Clock Input) :
D
1
D
0
The Rx/Tx tone programming and function inputs.
Programmed as shown in Table 2 these inputs will select
the CTCSS tone frequency and parallel or serial loading
function. Notone, when set in receive, enables the Rx
Audio Output and forces the Rx Tone Decode Output to a
logic '0,' in transmit the Tx Tone Output is held at V
BIAS
(Notone). These inputs each have an internal 1MΩ pullup
resistor. If FX375LG or LS package styles are used Pin 5
(Serial Enable 2) should be externally connected to V
SS
.
10
8
Rx Tone Decode Output :
The output of the decode comparator. In Rx a logic '0'
indicates 'CTCSS tone decoded' above the internal reference level, or Notone
programmed. This action internally enables the Rx audio path and Frequency Inversion
function (when applicable) as shown in Table 1. In Tx this output is a logic '1'.
11
9
Decode Comparator Input :
A logic '1' at this pin, in Rx, is compared internally with a
fixed reference level, a more positive input value will produce a logic '0' at the Rx Tone
Decode Output. This input should be externally connected to the Rx Tone Detect
Output via external integrator components C
7
, R
2
, R
3
, D
1
(see Figure 2).
12
10
Rx Tone Detect Output :
This output, in Rx, goes to a logic '1' when a valid,
programmed CTCSS tone is received at the Rx Tone Input. This input should be
externally connected to the Decode Comparator Input via external integrator
components C
7
, R
2
, R
3
, D
1
(see Figure 2).
13
–
Notone Output :
Outputs a logic '0' when a " Notone" CTCSS code has been
programmed . It can be used to operate squelch circuitry under receive "Notone"
conditions.
14
11
V
SS
:
Negative supply rail (GND).
The FX375LG and LS package styles are configured as a serial-data loading device,
Parallel Programing Inputs D
0
, D
1
and D
5
, and the N
OTONE
Output pin functions are not
available.
2
CMLMICRO [ CML MICROCIRCUITS ]
