Host Interface - Xerox WorkCentre Pro 412 Service Manual

Circuit Description

5-6 Host Interface

Referred to IEEE 1284 standard.
5-6-1. Host Interface
PARALLEL PORT INTERFACE PART KS32C61200 enables the parallel interface with the PC. This part is
connected to the PC through a Centronics connector. 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 Parallel Port Standard (http://www.fapo.com/ieee1284.html). In other words, it supports both
compatibility 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 PCs to transmit data to the printer. ECP mode is an improved protocol for the communication
between PC and peripherals such as printer and scanner, and it provides high speed two-way data com-
munication. ECP mode provides two cycles in the two-way data transmission; 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 it is useful for
the printer and scanner that need to transmit large raster images. 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 pro-
cessed.This system uses RLE for high speed data transmission. PC control signals 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.
Compatibility Hardware Handshaking Timing
5-54 3/03 WorkCentre Pro 412, FaxCentre F12 &
WorkCentre M15/M15i