Epson LX-300, Руководство по обслуживанию

Страница: 42 / 107

Operating Principles
LX-300 Service Manual
2.3
CONTROL CIRCUIT
control circuit consists of the board the major
(
components and explains how the board works.
2.3.1 Control
Circuit Operation Overview
The printer’s system contains a CPU at MHz, a gate array
(E05A79-type) and a main RAM ( 8KB It oversees of components in the
printer. The printer uses the E05A90 gate array to control address parallel
motor drive signals, etc. 2-5 shows of main and
Figure 2-18 shows the control circuits in block diagram form.
Table 2-8. Functions of the Main
Location
Function
CPU Block: Receives data from the host computer and sends it to the
input buffer in RAM (under interrupt processing control). Extends the
input data held in the buffer to create image data. Loads this image
data to the image buffer in RAM. Transfers the image data to the
printhead drive circuit. Also controls various parts of the printer
mechanism, such as PF motor control and color select motor control
SYSTEM
ICI
Gate Array Block: Controls the functions below.
Address decoding
. Parallel communications
●
Impact head drive control
. CR motor control
Main RAM Block: Holds the CPU area and various buffers.
ROM El
Contains the program that runs the CPU and holds the character
design (also called the character generator).
RESET A2 Hardware reset function
An electrically writable and erasable ROM used to hold such
information as the TOF and bidirectional adjustment value.
Serial l/F
Driver / receiver
SYSTEM
RESET
(lCl) 4
(AZ)
PROM RELEASE
(El)
LEVER
SENSOR
(OPTION)
. . . . . . . . . . . . . . . . . . .
Figure 2-12. Control Circuit Block Diagram
2-12