Host Interface - Xerox WorkCentre Pro 412 Service Manual

Circuit Description

5-4 Host Interface

Referred to IEEE 1284 standard.
5-4-1. 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 actu-
ate 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 communication. ECP mode provides
two cycles in the two-way data transmission; data cycle and command cycle. The command cycle has two for-
mats; 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 processed.This system uses RLE for high speed data trans-
mission. 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
5-22 WorkCentre Pro 412
August 2001
Launch Issue