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• Functional Description
The Cobra models MRF55 and MRF75 are Marine band FM Radio transceivers operated in the
frequency range 156.025MHz to 163.275MHz with WX and DSC. Functional as follows:
1. MRF55: Channel Up / Down, Emergency channel key CH16/9, WX/UIC key, Channel Scan key, TX
power HI/Low key, Dual watch channel key, Call/set key, Distress key, Squelch control volume, DC power
ON/Off and Audio Volume control, External Speaker Jack and GPS Jack, PTT key.
2. MRF75: Channel Up / Down, Emergency channel key CH16/9, WX/UIC key, MEMO Channel Scan key,
TX power HI/Low key, Tri watch channel key, Call/set key, Distress key, Squelch control volume, DC
power ON/Off and Audio Volume Up/Down control, PA Function, External Speaker & PA Jack and GPS
Jack, PTT key.
• MCU Description
The MCU uses Toshiba's TMP86CM47U micro-controller, there are 32k X 8bits ROM and 1k X
8bits RAM, LQFP44 pins package. These pin assignment as below table:
PIN
Description
1
Vss = GND
2
X-in, crystal 8 MHz
3
X-out, crystal 8 MHz
4
Test, connect to GND.
5
Vdd, +5VDC input
6
DC power on control
7
TX on/off control (on = low)
8
Reset pin
9
DC power on key scan
10
LCD backlight control
11
LCD backlight control
12
NMEA (GPS data) input
13
EEprom data pin
14
Volume down key scan
15
Volume up key scan
16
Squelch output control
17
Inhibit audio when DSC on
18
Control LCD driver A0 data pin
19
PLL STB. HI=F75, Low=F55
20
PLL clock data output
21
Beep tone generator
22
Control LCD CS1 pin
Remarks: MCU pin19 (BUS14) for MRF55 and MRF75 models select by resistor R371 and
R340 control. R371 open for MRF55 model, R340 open for MRF75 model selection.
Model PIN
55/75
23
Control LCD SDI data pin
55/75
24
WX alert data pin detect
55/75
25
TX Hi / low power control
55/75
26
Keys scan pin
55/75
27
Keys scan pin
F75
28
Beep tone Hi/low control
55/75
29
Digital volume data pin
55/75
30
Digital volume clock pin
F75
31
Open
55/75
32
EEprom clock pin
55/75
33
RX/TX signal indication
55/75
34
Pull high to +5VDC
55/75
35
AVDD (connect +5VDC)
F75
36
AVSS (connect to GND)
F75
37
Pin 37 to 41 for 1300Hz and
55/75
38
2100Hz FSK generator.
55/75
39
55/75
40
55/75
41
55/75
42
PLL data output
55/75
43
DSC detect pin
55/75
44
Squelch input detect
Description
Model
55/75
55/75
55/75
55/75
55/75
55/75
F75
F75
55/75
55/75
55/75
55/75
55/75
55/75
55/75
55/75
55/75
55/75
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