Xerox WorkCentre XK50cx, Service Manual

Page: 31 / 109

4-4
Circuit
DRAM CONTROLLER
As KS32C6400 has DRAM controller in it, DRAM
can be connected with external memory.
The control mode of DRAM controller enabling
EARLY WRITE, NORMAL READ, PAGE MODE, and
BYTE/HALF WORD ACCESS supports EDO DRAM
as well as normal DRAM. DRAM READ/WRITE
signals are /RD and /WR signals used to control
system buses. It supports CAS BEFORE RAS for
DRAM REFRESH and self-refresh mode for DRAM
backup. Connected with common /LCAS, /UCAS
and /RAS, it consists of 2 banks. Though each may
be connected with up to 1M - 4M halfword, one of
64bit is connected for this product.
PARALLEL PORT INTERFACE
This part connected with the computer through the
centronics connector makes possible parallel
interface with the computer. Data is transmitted
according to the standard of IEEE P1284. This MFP
controller supports compatibility mode the
traditional way to transmit print data, nibble mode
(4bit data) to upload data to the computer, and
duplex high-speed transmission with the computer
ECP (Extended Capabilities Port: 8bit data
transmission) all together.
It enables PC data to be printed and scanned data
to be uploaded quickly to the computer. Besides,
various data transmission and reception with the
computer such as uploading received fax data,
downloading fax data to be sent, and monitoring
system control signals and system conditions are
carried out here.
Fig.4-1-3 Compatibility Hardware handshaking Timing