Logic Circuits - Icom IC-706MKIIG Service Manual

• BFO frequency
RX BFO/3rd LO
Mode
frequency [MHz]
USB
9.0130
LSB
9.0100
9.0106
CW
(–CW pitch frequency)
9.0106
CW-R
(+CW pitch frequency)
9.008375 (2125 Hz tone)
RTTY
9.008885 (1615 Hz tone)
AM
No output
FM
9.4665 (3rd LO)
FM nar.
9.4650 (3rd LO)
WFM
No output
IF shift: Center, RTTY: Normal polarity

3-4 LOGIC CIRCUITS

3-4-1 BAND SELECTION DATA
(MAIN BOARD AND PLL UNIT)
To select the correct RF low-pass filter, high-pass filter and
VCOs on the PLL unit, the CPU outputs the following band
selection data from the I/O expander (MAIN board; IC2231,
IC2232), the D/A converter (MAIN board; IC2201) or DDS IC
(PLL unit; IC101) depending on the display frequency.
The D/A convertor output from IC2201 (pin 18) is doubled at
IC891d to obtain the band voltage for external equipment.
• Band selection data
IC2231,
IC2232
Frequency (MAIN)
[MHz]
HPF
BPF
0.03– 1.999999 L1
2.0– 3.999999 L2
4.0– 7.999999 L3
8.0– 10.999999
L4
11.0– 14.999999
15.0– 21.999999 L5
22.0– 29.999999 L6
30.0– 39.999999 B7W
40.0– 59.999999 B7
60.0–128.999999
129.0–143.999999
144.0–148.000000 B8
148.000001–
199.999999
400.000000–
B9
470.000000
TX BFO/FM PLL ref.
frequency [MHz]
9.0130
9.0100
9.0106
(–CW pitch frequency)
9.0106
(+CW pitch freqency)
9.0105 (MARK)
9.0100
9.0115 (PLL ref.)
9.0100 (PLL ref.)
No output
IC2201 IC101
(MAIN) (PLL)
LPF 1/2 band LPF
VCO
LPF voltage BPF
L1 3.70 V
L2 3.19 V
L3 2.68 V
0 V VCO1 LOF1
L4
2.18 V
L5 1.69 V
L6 1.19 V
L7 VCO2 LOF2
VCO1 LOF3
LOF4
0.96 V
L8 LOF5
VCO2
LOF4
B9 VCO3 LOF6
3-4-2 SUB CPU PORT ALLOCATIONS
(DISPLAY board; IC1)
Pin Port
number name
SFTL
1
18 PTTS
BU1S,
19, 20
BU2S
PHNK
80
81 RSK
96 PTTL
FUDL
97
98 AFGL
99 SQLL
3-4-3 I/O EXPANDER PORT ALLOCATIONS
(MAIN board; IC2221)
Pin Port
number name
MODS
4
5 AMS
6 FMS
7 WFMS
AFS1,
11, 12
AFS2
13 UNFM
14 MINH
3 - 8
Description
Input port for the [SHIFT] control.
Outputs a PTT signal.
Low : While transmitting.
Outputs displaly backlight control sig-
nal.
Input port for the [PHONES] jack con-
nection detection.
High : When the headphone or
external speaker is connected
to the [PHONES] jack.
Input port for the [RIT] switch.
Input port for the [PTT] switch on the
microphone.
Input port for the microphone up/down
signal.
Input port for the [AF] control.
Input port for the [RF/SQL] control.
Description
Outputs select signal for the Tx AF
selector switch (IC1141).
Hign : When AM and SSB modes
are selected.
Outputs AM mode select signal.
High : When AM mode is selected.
Outputs FM and FM-N modes select
signal.
High : When FM and FM-N modes
are selected.
Outputs WFM mode select signal.
High : When WFM mode is selected.
Output select signals for the Rx AF
selector switch (IC861).
MODE
PORT
WFM FM AM SSB/CW/RTTY
AFS1 High High Low
AFS2 High High Low
Outputs non-FM mode select signal.
High : When SSB/CW/RTTY/AM
modes are selected.
Outputs an audio mute signal for the
analog switch (IC971).
High : While transmitting
CW/RTTY modes.
Low
Low
in