Canon FAX-L260i Service Manual page 79

d-1) Modem IC (IC17)
A Rockwell R144EFXL PQFP is used as the MODEM IC. The MODEM IC carries out G3 modulation
conforming to ITU-T standards V.27ter, V.29, V.17 and V.33 on transmitted data received from the MPU
during transmission. During reception, the MODEM IC carries out G3 modulation on received signals
from the telephone line, according to the same standards.
d-2) ROM (IC5)
This 8Mbit ROM contains the control programs (e.g. communications section etc.)
d-3) DRAM (IC6)
This 4Mbit DRAM is used as a temporary location to house image data when decoding/encoding image
data and performing resolution exchange when data is being transmitted.
d-4) MPU (IC7)
The main function of the NEC UPD70741GC-25-7EA are as follows:
•32 bit CPU
•24 bit address bus
•16 bit data bus
•DMA control
•A/D converter
•Software CODEC
•Interrupt control unit
d-5) PCM CODEC IC (IC19)
This IC converts the analog signal sent from a G3 modem into a digital signal when transmitting with G3.
Also, when receiving with G3, it converts the received digital signal into an analog signal.
d-6) Multi-protocol serial controller IC (IC20)
This IC performs parallel/serial conversion of D-channel (Layer 3) data, and each B-channel data when
transmitting with G4, between the DRAM (IC6) and the ISDN interface IC (IC26) interface, and per-
forms parallel/serial conversion of B-channel data when transmitting with G3 between the DRAM (IC6)
and the modem (IC7). It also performs ISDN interface IC (IC26) and HDLC (High level Data Link
Control procedures) when handling D-channel (Layer 3) data, B-channel data when transmitting with
G4, and image data when transmitting with G3 (ECM).
d-7) DMA controller IC (IC23)
Performs DMA (Direct Memory Access) control between the DRAM (IC6) and the Multi-protocol serial
controller IC (IC20) when transmitting with G4/G3.
d-8) ISDN interface IC (IC26)
This YAMAHA-made IC YM7405C has Layer 1 functions, Layer 2 functions (LAPD), and Layer 3
interface functions for connection to an ISDN circuit.
d-9) Transformer (T1, T2)
Used to provide insulation between the ISDN circuit and the main unit, as well as to satisfy electric
characteristics of the ISDN circuit.
FAX-L260i Chapter 2: Technical Reference
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