MRC MCX-5000 Series, Manual

Page: 40 / 220

MARINE RADIO CO.,LTD.
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선박무선
Subject : Auto Exchanger Page : (39 / 46)
Date : 2010.10.13 Doc. : MCX-5000S_ENG_R1
(QAS-ADD-008/1/10.10.13) manual\pabx\mcx-5000S\MCX-5000S_eng.doc
( MARINE RADIO CO., LTD.) MRC
2. Explanation of Circuit
2.1 Configuration of System
An auto-exchanger for the MCX - 5000 series includes power source unit, switching regulator
unit, CPU board, dial tone board, trunk board, I/O switching board, display board etc.
1. Except for switching regular unit and display board, the main devices make replacement
and maintenance easily because they support plug-in.
The following figure shows the signal flow of each device:
2.2 CPU Board
The CPU board controls the overall system. 8085 Micro-Processor performs all functions by program
in system ROM. Timer sets time for morning call, and CPU reads time data and uses them as a variety
of time information. This time information is operated by built-in battery even during power failure.
Also, it is transmitted to display board through buffer. The Watch Dog circuit is automatically
initialized if the failure is generated in program, so it recovers the system normally. CPU monitors
the selected I/O board through card select port, address bus and control signal port. At this
time, if any subscriber picks up the handset, it is detected by data bus and operated in order of
program. The following figure shows the detailed flow of CPU board: