Icom IC-775 Service Manual

4-5
LOGIC
CIRCUITS
4-5-1
BAND
SELECTION
DATA
(RF,
MAIN,
FILTER
AND
PLL UNITS)
To
select
the
correct
bandpass
filter,
low-pass filter
and
VCOs
on
the RF,
FILTER
and PLL
units, the CPU
outputs
the
following
band
selection
data from
the I/O
expander (RF
unit
IC1, IC2;
FILTER
unit IC1),
the A/D
converter
(MAIN
unit
IC13)
or DOS
ICs
(PLL
unit IC1, IC4)
depending
on the
displayed
frequency.
The A/D
converter
output
from IC13
pin 13 is
doubled by 2
at
IC15a to
obtain the
band
voltage for
external
equipment.
Band selection
data
Frequency
IC1,
IC2
(RF)
IC13
(MAIN)
IC1
(FILTER)
IC1
(PLL)
IC4
(PLL)
(MHz)
BPF
1/2
band
voltage
LPF
A
VCO
B
VCO
0.1-0.49999
B1
0.5-1 .59999
B2
3.71 V
LI
1
.6-1
.99999
B3
2.0-2.99999
B4
3.18 V
L2
VIA
VI
B
3.0-3.99999
B5
4.0-5.99999
B6
2.67
V
L3
6.0-7.99999
B7
8.0-10.99999
B8 OV
L4
V2A V2B
11.0-14.99999
B9
2.17 V
L5
15.0-21.99999
BIO
1.69 V
L6
V3A V3B
22.0-29.99000
B11
1.19
V L7
V4A
V4B
4-5-2
MAIN CPU
PORT
ALLOCATIONS
(MAIN
UNIT IC12)
Pin
number
Port name
Description
14
IKEY
(P23)
Output
port for
the internal
antenna
tuner.
15
ISTA
(P24)
Input
port for the
internal
antenna
tuner.
19
CK
(P30)
Outputs a
clock signal
for the I/O
expanders,
optional UT-66,
etc.
21
DATA
(P32)
Outputs serial
data for the I/O
expanders,
optional UT-66,
etc.
55
DUT
(P73)
Input
port for the
DSP unit
installation.
60
POE
(P80)
Outputs
an
enable signal for
the
PLL
strobe expander 1C
(IC13).
61 PST1
(P81)
Outputs a
strobe
signal for the
PLL
strobe expander 1C
(IC13).
62
PST2
(P82)
Outputs
a strobe
signal for the
expander
1C
(IC14) in the
PLL
unit.
63
PCK
(P83)
Outputs a
clock signal
for the DDS
ICs
and PLL
ICs.
64
PDAT
(P84)
Outputs
serial data
for the DDS
ICs
and PLL ICs.
66
SQL
(P86)
Outputs
a squelch
control
signal.
72
SBSY
(P94)
Input
port for the
optional UT-66
busy
signal. This port
becomes
“High” during
speech
synthesis.
73 SST
(P95)
Outputs a
strobe signal
for the
optional UT-66.
75 CSEN
(P97)
Outputs
an automatic
tuning
signal
to
the
internal antenna
tuner.
78 BEEP
(P11)
Outputs beep
tone signals.
86
CIR
(P41)
Input port for
Cl-V bus line.
87 CIT
(P42)
Output
port for Cl-V
bus line.
90
TRC
(PBO)
Input port for
transmit/receive
switching
signals. This
port
becomes
“Low” while
transmitting.
91
AMET
(PB1)
Input
port for meter
signal level.
92
ASQN
(PB2)
FM
noise
level input for
squelch
control.
93
SQLV
(PB3)
S-meter
level input for
squelch
control.
94
AMIC
(PB4)
Input
port for
microphone up/down
switches.
4-11

Icom IC-775 Specifications

General

Brand	Icom
Model	IC-775
Category	Transceiver
Language	English