Control Circuit; Control Circuitoderation Overvie W - Epson LQ-300 Service Manual

Operating Principles

2.3 CONTROL CIRCUIT

The control circuit consists of the C143 MAIN board assembly. This section desuibes the major
components and explains how the board works.
Control Circuit Operation Overview
2.3.1
The printer has a CPU (TMP90C041) that runs at 9.8304 MHz, a gate array (E05B02-type), a
printer. The printer uses the E05B02 gate array to control memory management, parallel
communications, PF motor drive signals, etc. Table 2-8 shows functions of ICS and circuits. Figure
2-12 shows the control circuits in bl&k diagram form.
CPU
I
I
A
Panel
Gate Array
Parallel l/F
Serial l/F
Figure 2-12. Control Circuit Block Diagram
2-12
Table 2-8. Functions of the Main IC
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.
Controls the functions below:
Input/Output Control
Memory Management
. Bit Manipulation
Interface Control
. Expanded Parallel Port
. Printhead Control
Motor Control
An electrically writable and erasable ROM used to hold such
information as the TOF position and bidirectional adjustment value.
Driver / receiver
Hardware reset function
Power off detection
Contains the program that runs the CPU and holds the character
design (also called the charaoter generator).
Input buffer
1
Sensor
I L
RESET
Color Ribbon
Function
Power Off Sensor
+35 V Sensor
PE Sensor
4
p
' "
4
Release Lever Sensor
A
Sensor
1