Gp 15 Host Interface - Xerox WorkCentre M20 Service Manual

Figure 3 Block Diagram of CIP4
General Procedures and Information
GP 14, GP 15

GP 15 Host Interface

Purpose
To give information about the machines interfaces:
• Host Interface
• USB Interface (Option: Direct Kit/Network Kit)
Referred to IEEE 1284 standard.
NOTE: If necessary, refer to GP 20 for the acronym list and cross reference lists of more com-
monly recognised part names.
Host Interface
PARALLEL PORT INTERFACE PART ARM946ES has the Parallel Port Interface Part that
enables Parallel Interface with a PC. This part is connected to a PC through a Centronics con-
nector. It generates major control signals that are used to actuate parallel communication. It is
comprised of /ERROR, PE, BUSY, /ACK, SLCT, /INIT, /SLCTIN, /AUTOFD and /STB. This part
and the PC data transmission method support the method specified in IEEE P1283 Paral-
lel Port Standard (http://www.fapo.com/ieee1284.html). In other words, it supports both com-
patibility mode (basic print data transmitting method), the nibble mode (4bit data; supports
data uploading to PC) and ECP (enhanced capabilities port: 8bits data - high speed two-way
data transmission with PC).
Compatibility mode is generally referred to as the Centronics mode and this is the protocol
used by most PC's to transmit data to a printer. ECP mode is an improved protocol for the com-
munication between a PC and peripherals such as a printer and a scanner, and it provides high
speed two-way data communication. ECP mode provides two cycles in the two-way data trans-
mission; data cycle and command cycle. The command cycle has two formats; Run-Length
Count and Channel Addressing. RLE (Run-Length Count) has high compression rate (64x)
and it allows real-time data compression that is useful for the printer and scanner that need to
transmit large raster image that has a series of same data. Channel Addressing was designed
to address multiple devices with single structure. For example, like this system, when the fax/
printer/scanner have one structure, the parallel port can be used for other purposes while the
printer image is being processed. This system uses RLE for high speed data transmission.
PC control signal and data send/receive tasks such as PC data printing, high speed uploading
of scanned data to PC, upload/download of the fax data to send or receive and monitoring the
system control signal and overall system from PC are all processed through this part.
USB Interface (Option: Direct Kit/Network Kit)
Refer to Figure 1.
March 2004
6-26 Work Centre M20 Family