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5-4 BRC-300/300PBRU-300/300P5-2. BRU-300/300P Circuit Description5-2-1. MC-66 BoardThe MC-66 board is the core board of BRU-300/300P.Optical Communication InterfaceThe laser transceiver unit receives camera image data, syncsignals, character data, several clocks (54, 27, 13.5, and6.75 MHz), and serial control data transmitted from theBRBK-303 installed in BRC-300/300P through an opticalfiber cable, and then converts the optical signal to electri-cal signals. Then the gigabit transceiver IC4401 convertsthe serial electrical signals to parallel signals. Next, thedemultiplexers IC4407 to IC4412 decodes multiplexedsignals to restore camera signals.The gigabit transceiver converts clock and control signalsgenerated in BRU-300/300P to serial signals, and the lasertransceiver unit converts electrical signals to optical signal.The converted optical signal is then transmitted to theBRBK-303 in BRC-300/300P with an optical fiber cable.Video Signal ProcessingThe digital encoder IC3018 encodes restored 13.5 MHzrate Y data and CbCr data to composite, Y and C signalsusing the 27 MHz clock and H SYNC/V SYNC signals,and then converts the digital signals to analog composite,Y and C signals.IC3018 also superimposes the character data (generated inBRC-300/300P or by IC3506 on this board) with videodata for menu display.Synchronization and ClockIC3001 detects whether the EXT SYNC signal has beeninput or not, and lets the signal generator locking driverIC3009 recognize external synchronization or internalsynchronization.When the EXT SYNC signal has been input (externalsynchronization), IC3009 phase-compares the H REFsignal sent from BRC-300/300P with the EXT SYNCsignal to control the 54 MHz VCO X3001. The crystaloscillator X3003 (or X3002 in PAL system) generatesclock for the signal generator locking driver (BRU-300:14.31818 M Hz, BRU-300P: 14.1875 MHz).When the EXT SYNC signal has not been input (internalsynchronization), the microcomputer IC3518 and the INTVCO CONT signal sent from the D/A converter IC3008control the 54 MHz VCO X3001.The 54 MHz VCO output is used as the clock of thegigabit transceiver IC4401. The BRBK-303 in BRC-300/300P restores 54 MHz clock as the reference signal ofBRC-300/300P from the signal that is input through anoptical fiber cable.The NTSC/PAL mode setting switch S3001-2 is set forBRU-300 or BRU-300P. The NTSC/PAL switching signalis sent to the digital encoder, microcomputer, BRBK-301,BRBK-302, and BRBK-304, as well as to the sync signalgenerator circuit for setting a BRU-300/300P operationmode.Control SystemThe microcomputer IC3518 sends/receives commands andstatus data to/from internal and external circuits using theVISCA protocol. It controls the digital encoder on the MC-66 board with the IIC serial data communication.IC3512 and IC3514 are transceivers operating on theVISCA protocol. IC3512 is used for the RS-232C interfaceand IC3514 for the RS-422 interface. The microcomputercontrols data communication according to baud rate of9600 or 38400 bps. Selection of RS-232C or RS-422 andselection of baud rate (9600 or 38400 bps) are set by theDIP switch on the SW-1207 board, and are input to themicrocomputer. These selections are also provided forBRC-300/300P and RM-BR300. Both selections shall bethe same in all these three units.Camera address is also set by the same DIP switch, and isinput to the microcomputer.The menu displaying character generator IC3506 iscontrolled by the microcomputer. The character data issuperimposed with video data by the digital encoder.EEPROM IC3501 saves data (preset position, etc.) thatmust be retained even during power OFF.Power Supply CircuitThe AC-DC converter generates +12 V DC from the ACpower that is input into the AC inlet, and supplies the+12 V DC to the MC-66 board.The DC-DC converter IC4001 on the MC-66 boardgenerates DC voltages required in BRU-300/300P.The PWRC CAM signal, which is the BRU-300/300Pstartup information, set the optical output of the lasertransceiver unit to ON/OFF for drive BRC-300/300P intothe ON/STANDBY state in conjunction with BRU-300/300P.The POWER indicator (LE-281 board) on the front panel,which is controlled by the microcomputer, shows powercondition. It lights up in green during normal operation,and flashes in red when an error occurs.