Xerox WorkCentre Pro 412 Service Manual page 43

Circuit Description
5-2-6 FS781 (Frequency Attenuator)
This system used FS741 for the main clock for EMI suppression.
It spreads the source clock in a consistent bandwidth to disperse the energy gathered in order to attenuate the
energy.
The capacitor value of the loop filter (PIN 4) is set depending on the source clock used or the spread band-
width. Refer to FS781 Spec. for detail.
5-2-7 USB (Universal Serial Bus)
NS's USBN9602 is used as the interface IC and 48MHz clock is used.
When the data is received through the USB port, EIRQ1 SIGNAL is activated to send interrupt to CPU, then
it directly sends the data to DRAM by IOCS4* & DRAMA(11) SIGNAL through DRAMD (24;31).
5-2-8 SRAM; 32KB SRAM
It stores a variety of option data.
5-2-9 FAX Transceiver
5-2-9-1. General
This circuit processes transmission signals of modem and between LIU and modem.
5-2-9-2. Modem (u44)
FM336 is a single ship fax modem. It has functions of DTMF detection and DTMF signal production as well as
functions of modem. TX A1, 2 is transmission output port and RX IN is received data input port. / POR signal
controlled by MFP controller (U3:KS32C61200) can initialize modem (/M_RST) without turning off the system.
D0-D7 are 8-bit data buses. RS0-RS4 signals to select the register in modem chips. /RS and /WR signals
control READ and WRITE respectively. /IRQ is a signal for modem interrupt.
Transmission speed of FM336 is supported up to 33.6k.
The modem is connected to LINE through transformer directly.
FAX TRANSCEIVER
WorkCentre Pro 412 5-17
August 2001
Launch Issue