Icom IC-F70DT, Service Manual

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4 - 5
BPF
From FM IF IC
(IC3, pin 11)
To AF volume
From
MIC amplifier
(IC203; FRONT UNIT)
To FM/PM SW
(IC302, pin 5)
• DIGITAL MODE BLOCK DIAGRAM
DSP UNIT
AMP
AMP
Q303
IC302
RECEIVED SIGNAL
FI1
IC5
IC8
IC7
IC9
IC9 IC4
IC302
IC301
A/D
LINER
CODEC
IC
LINER
CODEC
IC
BASE
BAND
IC
DIG/ANA
SW
DSP
IC
MIC SW
LPF
TRANSMIT SIGNAL
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).
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).
4-6 PORT ALLOCATIONS
4-6-1 CPU (IC307)
Pin
number
Port
name
Description
4–7
R1, R2,
R4, R8
Input ports for rotary selector (VR
UNIT; S1).
10 SSO
Outputs serial data to the PLL IC (IC1,
pin 15) and D/A converter (IC303, pin 8).
11 SCK
Outputs clock signal to the PLL IC (IC1
pin 14) and D/A converter (IC303, pin 7), etc.
13 PLST
Outputs strobe signals to the PLL IC
(IC1, pin 16).
15 DASW
Outputs control signal to the digital
/analog switch (IC302).
Low:
While analog mode is selected.
16 TXC
Outputs the T5V switch (Q305) con-
trol signal.
Low:
During transmit.
17 TMUT
Outputs the ALC amplifi er (IC5) con-
trol signal.
Low:
During receive.
18 AFON
Outputs control signal for AF mute
circuit (FRONT UNIT; IC205) and AF
power amplifi er (FRONT UNIT; IC201).
High:
AF amplifi er (IC201) is activated.
19 NWC
Outputs wide/narrow switch (D13,
D14) control signal.
High:
When narrow mode is selected.
Pin
number
Port
name
Description
20 DDSD
Input port for serial data from the
DTMF decoder IC (IC300, pin 9).
21 DDAC
Outputs clock signals to the DTMF
decoder IC (IC300, pin 10).
26 R5C
Outputs R5V switch (Q306) control signal.
High:
While receiving.
27 S5C
Outputs S5V switch (Q304) control
signal.
High: In power save mode..
29 PTTO
Input port for optional unit.
Low:
Switch ON.
30 EM
Input port for the emegency switch
(FRONT UNIT; S117).
Low:
While emegency switch is
pushed.
32 RMUT
Input port for the AF mute signal from
the optional unit via J1 or J2.
Low:
While RX audio is muted.
33 MMUT
Input port for the microphone mute
signal from the optional unit via J1 or
J2.
Low:
While microphone audio is
muted.
34–36
OPT1–
OPT3
I/O ports for the connected optional
unit to J1.