![background image](http://html.mh-extra.com/html/icom/ic-2820h/ic-2820h_service-manual_612070015.webp)
4 - 9
4-5 CPU PORT ALLOCATION
PIN
No.
PORT NAME
DESCRIPTION
I/O
3
AN
Cut-off frequency shifting signal to the HPF
(IC48).
O
4
DA_SEL
Cut-off frequency shifting signal to the HPF
(IC48).
O
5
MM_MUTE
MIC mute signal to the MIC mute switch (IC30).
“H”=MIC mute.
O
6
DCONT
ALC amplifier control signal tot the AF
switches (IC29 and IC52).
“H”=ALC amplifi er ON.
O
7
R_WN_SEL
2nd IF filter (Right band; Wide/Narrow)
toggling signal.
“H”=Narrow. "L”=Wide.
O
11
MIC_SENC
Microphone sensitivity select signal.
“H”=High sensitivity.
O
17
MOD_DA
M o d u l a t i o n l i n e sw i t c h i n g s i g n a l t o
t h e M O D s e l e c t o r ( L e f t b a n d ; I C 9 ) .
“H”=Modulation enable.
O
18
MODSEL
M o d u l a t i o n l i n e sw i t c h i n g s i g n a l t o
the MOD selector (Right band; IC63).
“H”=Modulation enable.
O
21
R_PLLSTB
Strobe signal to the PLL IC (Right band;
IC14).
O
22
L_PLLSTB
Strobe signal to the PLL IC (Left band;
IC41).
O
23
L_AMC
AM-demodulator circuit (Left band) control
signal.
“H”=AM mode (AM-modulator circuit is
activated).
O
24
DTCS_SEL
Tone filter switching signal to the LPF
(Q100).
“H”=DTCS mode. “L"=CTCSS mode.
O
25
L_R5C
RX circuits (Left band) control signal.
“H”=RX circuits (Left band) is activated.
O
26
L_WN_SEL
2 n d I F f i l t e r ( W i d e / N a r r ow ) t o g g l i n g
signal.(Left band)
“H”=Narrow. “L”=Wide."
O
27
UMMUTE
Modulation mute signal to the MOD
m u t e s w i t c h ( R i g h t b a n d ; Q 6 4 ) .
“H”=Modulation muted.
O
28
UTX_C
Transmitting control signal to the VT8
regulator (Q12, 15).
O
29
L_VCO_SHIFT
VCO oscillating frequency shift signal to
the Left band VCO.
O
30
R_PLLSW
Lock-up time control signal to the loop fi lter
(Right band).
“H”=Fast lock-up time.
O
31
R_UNLOCK
PLL unlock signal from the PLL IC (Right
band; IC14).
I
32
PLLCK
Clock signal to the PLL ICs (Right band;
IC14, Left band; IC41).
(Commonly used for both of the Left and
Right bands.)
O
33
PLLDATA
Data to the PLL ICs (Right band; IC14, Left
band; IC41).
(Commonly used for both of Left and Right
bands.)
O
34
L_UNLOCK
PLL unlock signal from the PLL IC (Left
band; IC41).
I
35
VMMUTE
Modulation mute signal to the MOD
m u t e s w i t c h ( L e f t b a n d ; Q 1 0 9 ) .
“H”=Modulation muted.
O
36
VTX_C
Transmitting control signal to the UT8 regulator
(Q13, 17).
“H”=While transmitting.
O
37
L_PLLSW
Lock-up time control signal to the loop fi lter
(left band).
“H”=Fast lock-up time.
O
PIN
No.
PORT NAME
DESCRIPTION
I/O
38
R_UVCO_SEL
VCO power control signal to the VCO
select switch (Right band UHF; Q65, 68).
“L”=Right band TX/RX VCO is activated.
O
39
R_VVCO_SEL
VCO power control signal to the VCO
select switch (Right band VHF; Q65, 68).
“L”=Right band RX VCO is activated.
O
40
L_LO_SW
L O f i l t e r sw i t c h i n g s i g n a l t o t h e L O
regulator (Q106).
O
42
R_DA_SEL
AF line switching signal to the AF switch
(IC12).
O
42
R_AFFIL_SEL
Switching signal to the AF filter (Right
band; Q48).
O
43
R_DET_MUTE
AF line switching signal to the AF switch (IC16).
“H”=AF mute.
O
44
L_DA_SEL
AF line switching signal to the AF switch
(IC11).
O
45
L_DET_MUTE
AF line switching signal to the AF switch (IC13).
“H”=AF mute.
O
48
D5VC
Power control signal for the optional unit.
O
51
R_AF_MUTE
AF mute signal to the SP mute switch (Right
band; Q101).
“H”=AF mute.
O
52
L_AFFIL_SEL
Switching signal to the AF fi lter (Left band;
Q47).
O
53
DA3STB
Strobe signal to the D/A converter.
O
53
DA2_STB
Strobe signal to the electric volume.
O
55
DTCS
DTCS signal.
O
56
DTMF
DTMF signal.
O
57
MIC_SEL
Connected microphone detect signal.
I
61
DTMSTB
Strobe signal to the DTMF decoder (IC56).
-
62
MICUD
[UP]/[DWN] key input.
I
63
R_RSLV
While receiving; inputs RSSI signal (IC18;
Right band).
While transmitting; inputs Lock Voltage
from the PLL IC (IC14).
I
64
L_RSLV
While receiving; inputs RSSI signal from IF
ICl (IC15; Left band).
While transmitting; inputs Lock Voltage
from the PLL IC (IC41).
I
65
IDET
Current level from the current detector
(IC55, Q164).
I
68
R_DTCS_IN
Demodulated DTCS signals from the
CTCSS fi lter (Q42).
I
70
L_DTCS_IN
Demodulated DTCS signals from the
CTCSS fi lter (Q41).
I
71
TEMP
Transceiver's internal temparature from the
thermal detector circuit (R509).
I
76
SCL
I/O port for clock signal to the EEPROM
(IC22).
I/O
77
AF_VOL_CK
Serial clock signal to the electric volume
IC.
O
78
AF_VOL_DATA Data signal to the electric volume IC.
O
79
AF_VOL_STB
Latch enable signal to the electric volume
IC.
O
80
AF_VOL_RES Reset signal to the electric volume IC.
O
80
PWR
Power control signal to the PWR controller
(Q82).
“H”=While the power is ON.
O
82
SDA
Data signal to the EEPROM (IC22).
I/O
83
L_AF_MUTE
AF mute signal to the SP mute switch
(Q102).
O
85
MIC_PTT
Input port for [PTT] key on the connected
microphone.
I