Samsung ML-920 Service Manual page 157

3-4 HOST INTERFACE:
Referred to IEEE 1284 standard.
3-4-1. HOST INTERFACE
PARALLEL PORT INTERFACE PART KS32C61200 has the Parallel Port Interface Part that enables Parallel Interface with
PC. This part is connected to PC through 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 PC to trans-
mit data to the printer. ECP mode is an improved protocol for the communication between PC and peripherals such as print-
er 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 formats; Run-Length Count and Channel Addressing. RLE (Run-Length Count) has high com-
pression rate (64x) and it allows real-time data compression that it 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 sin-
gle structure.
For example, like this system, when the fax/printer/scanner have one structure, the parallel port can be used for other pur-
poses while the printer image is being processed.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.
PPD( 7: 0)
BUSY
nSTROBE
nACK
Samsung Electronics
DATA
<Compatibility Hardware Handshaking Timing>
- This Document can not be used without Samsung's authorization -
CIRCUIT DESCRIPTION
Repair Manual
3-27