Xerox WorkCentre M20 Service Manual page 167

Figure 2 Program operation timings
NOTE: 1. PA= program address, PD= program data, Dout is the true data at the program
address.
NOTE: 2. Figure 2 shows device in word mode.
Figure 3 BYTE# timings for write operations
Work Centre M20 Family
NOTE: Refer to the Erase/Program Operations table for Tas and Tah specifications
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 the CPU, then
it directly sends the data to DRAM by IOCS4*&DRAMA (11) SIGNAL through DRAMD (24;31).
SRAM: 1MByte SRAM K6F1008U2C
It stores a variety of option data.
FAX Transceiver
General
This circuit processes transmission signals of modem and between LIU and modem.
Modem (U44)
FM336 is a single ship fax modem. It has functions of DTMF detection and DTMF signal pro-
duction as well as functions of a modem. TX A1, 2 is a transmission output port and RX IN is a
received data input port. / POR signal controlled by MFP controller (U3:ARM946ES) can initial-
ize modem (/M_RST) without turning off the system. D0-D7 are 8-bit data buses. RS0-RS4 sig-
nals 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, refer to Figure 4.
Figure 4 Fax transceiver
March 2004
6-23
General Procedures and Information
GP 13