43471801TH Rev.1
8 /
Oki Data CONFIDENTIAL
2.2
Circuit Operation (See Figure 1)
The circuit of this printer consists of the control board and carriage board.
Circuits such as
µ
CPU and its peripheral circuits, drive circuits, and the external interface circuit are set
on the control board.
The switches and LED are set on the control board.
With the control board being the main board, the boards are connected by cables.
2.2.1 CPU and peripheral circuits
(1)
CPU (MSM67
×
640)
The CPU is a 16-bit one-chip CPU which operates the peripheral circuits. Each I/O port is set
as ADDRESS - BUS, DATA - BUS, and various control lines. It is capable of 4-channel A/D
converter input and has five timers.
(2)
Program ROM (Flash ROM)
The control program of the printer is stored.
µ
CPU operates according to the contents and
various controls are performed.
(3)
Printer Butter etc (D-RAM)
This is used to store various data for data received in 4Mbit RAM or print buffer, etc.
(4)
LSI (MG74Q514-131)
This is an LSI exclusively for the print head controller, external interface, and motor control. It
has the following functions.
(a) Print head data control
Print data is unarchived to the print timing of a disperse allocation head and controls 24-pin
worth of impact data drive time.
(b) Dot timing generating function
Dot timing (IPT) in sync with the print speed is generated and notifies the information to
CPU.
(c) Speed control function of the space motor
The speed of the space motor is controlled and input command from CPU. Furthermore,
the space motor speed in various print modes are also controlled.
(d) Parallel interface function
IFD 1-8 are used as input/output data of parallel data. Parallel data sent from the interface
connector is latched by strobe signal STB-N and is read into CPU by a RD signal.
Furthermore, control signals such as BSY-N, ACK, PE-N, and SEL-N are output to the
interface connector by WR signals.
(e) I/O port
The I/O port has 14-bit input/output ports and controls various signals by input command
from CPU.
(5)
Download ROM (EPROM)
Use when update the Flash-ROM program. Usually nonimplement.
