Canon fax basic 2000 서비스 매뉴얼

FACSIMILE SYSTEM

6–32

7. G4CNT BOARD

The G4CNT board is provided on G4 facsimiles, and is the equivalent to

the NCU board on a G3 facsimile. The G4CNT board performs connection

with the ISDN line to perform digital communications. In the case of a G4

facsimile, G4 communications is performed. In the case of a G3 facsimile,

digital signals are converted to analog signals at reception and analog sig-

nals are converted to digital signals at transmission by the PCM 

and MODEM on the G4CNT board to perform G3 communications.

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The G4CNT board comprises the following ICs.

As the block diagram below shows an example where two lines can be

used simultaneously, two MODEMs are provided.

The G4CNT board has a CPU (V821) for controlling the entire G4CNT

and a slave CPU (V853). The slave CPU performs coding (MR, MMR or

JBIG) on the MR data stored in DRAM matched to the functions of the

machine at the other party, and during reception codes the coded data from

the other party to MR data for storing on DRAM.

• ISDN interface

As its name implies, this interfaces the facsimile with the ISDN line, and

performs outgoing/incoming call control and layer 1 control (extraction of

data and synchronization).

• HDLC controller

This controller converts data to HDLC format and performs serial/parallel

conversion to enable detection of data errors.

• SLIC

This functions as an 

 when an analog telephone is connected to

the facsimile. For this reason, it forms the DC loop with the analog tele-

phone and detects the off-hook state of the telephone.

• Dual port RAM

This RAM is for separating the V821CPU and V853 slave CPU systems.