Digital Circuit (Ic-F70Dt/Ds Only); Port Allocations - Icom IC-F70DT Service Manual

4-5 DIGITAL CIRCUIT (IC-F70DT/DS only)

• WHILE RECEIVING
A portion of the 2nd IF sigal from the limiter amplifier section
in the FM IF IC (IC3) is output from pin 11 and is applied to
the 2nd IF amplifier (Q303). The amplified 2nd IF signal is
applied to the DSP UNIT via J2 (pin 11).
The 2nd IF signal from the MAIN UNIT is passed through
the ceramic BPF (DSP UNIT; FI1) to suppress heterodyne
noise, and amplified again at the digital IF amplifier (DSP
UNIT; IC5, pin 4). The amplified 2nd IF signal is applied to
the A/D converter (DSP UNIT; IC8, pin 3) to be converted
into digital IF data, then applied to the DSP IC (DSP UNIT;
IC7). The DSP IC converts the digital IF into the digital audio
signal.
The digital audio signal from the DSP IC are converted into
analog audio signals at the LINER CODEC IC (IC9) and out-
put from pin 16. The audio signals from the LINER CODEC
IC are applied to the MAIN UNIT via J1 (pin 22).
• DIGITAL MODE BLOCK DIAGRAM
RECEIVED SIGNAL
From FM IF IC
AMP
(IC3, pin 11)
Q303
To FM/PM SW
MIC SW
(IC302, pin 5)
IC302

4-6 PORT ALLOCATIONS

4-6-1 CPU (IC307)
Pin Port
number name
Input ports for rotary selector (VR
R1, R2,
4–7
UNIT; S1).
R4, R8
Outputs serial data to the PLL IC (IC1,
10 SSO
pin 15) and D/A converter (IC303, pin 8).
Outputs clock signal to the PLL IC (IC1
11 SCK
pin 14) and D/A converter (IC303, pin 7), etc.
Outputs strobe signals to the PLL IC
13 PLST
(IC1, pin 16).
Outputs control signal to the digital
15 DASW /analog switch (IC302).
Low: While analog mode is selected.
Outputs the T5V switch (Q305) con-
16 TXC trol signal.
Low: During transmit.
Outputs the ALC amplifi er (IC5) con-
17 TMUT trol signal.
Low: During receive.
Outputs control signal for AF mute
circuit (FRONT UNIT; IC205) and AF
18 AFON
power amplifi er (FRONT UNIT; IC201).
High: AF amplifi er (IC201) is activated.
Outputs wide/narrow switch (D13,
19 NWC D14) control signal.
High: When narrow mode is selected.
DSP UNIT
BPF
A/D
AMP
IC5
IC8
FI1
LPF
IC4
Description
The audio signals from the DSP UNIT are applied to the
base band IC (MAIN UNIT; IC301, pin 20) after being
passed through the digital/analog switch (MAIN UNIT; IC302 ).
• WHILE TRANSMITTING
The microphone signals from the base band IC (IC301, pin 7)
are applied to the DSP UNIT via J2 (pin 4).
The microphone signals from the MAIN UNIT are applied
to the LINER CODEC IC (DSP UNIT; IC9, pin 2) to convert
into the digital audio signal.
The converted digital audio signal is processed by the DSP
IC (DSP UNIT; IC7), and applied to the LINER CODEC IC
(DSP UNIT; IC9) again. The signal from the LINER CODEC
IC (IC9, pin 15) is passed through the LPFs (DSP UNIT;
IC4, pins 3, 4, 5, 7) and applied to the MAIN UNIT via J1,
and then passed through the microphone switch (MAIN
UNIT; IC302, pins 3, 4), FM filter (R328, C335), FM/PM
switch (IC302, pins 2, 15).
IC7
DSP
DIG/ANA
LINER
IC
CODEC
IC
IC302
IC9
LINER
CODEC
IC
IC9
Pin Port
number name
20 DDSD
21 DDAC
26 R5C
27 S5C
29 PTTO
30 EM
32 RMUT
33 MMUT
OPT1–
34–36
OPT3
4 - 5
To AF volume
SW
BASE
BAND
From
IC
MIC amplifier
(IC203; FRONT UNIT)
IC301
TRANSMIT SIGNAL
Description
Input port for serial data from the
DTMF decoder IC (IC300, pin 9).
Outputs clock signals to the DTMF
decoder IC (IC300, pin 10).
Outputs R5V switch (Q306) control signal.
High: While receiving.
Outputs S5V switch (Q304) control
signal.
High: In power save mode..
Input port for optional unit.
Low: Switch ON.
Input port for the emegency switch
(FRONT UNIT; S117).
Low: While emegency switch is
pushed.
Input port for the AF mute signal from
the optional unit via J1 or J2.
Low: While RX audio is muted.
Input port for the microphone mute
signal from the optional unit via J1 or
J2.
Low: While microphone audio is
muted.
I/O ports for the connected optional
unit to J1.