Main Control Board - Oki OKIPAGE 8z Service Manual

2.1 Main Control Board

The main control board consists of a one-chip CPU, a program ROM, a DRAM, an EEPROM, a host
interface circuit, and a mechanism driving circuit. The mechanism driving circuit consists of an LED head,
a main motor, and an electromagnetic clutch.
(1) One-chip CPU
The one-chip CPU is a custom CPU (8-bit internal bus, 8-bit external bus, 16-MHz clock) incorporating
mask ROM and CPU peripheral devices. This CPU has the functions listed in the table below.
Built-in Device
DRAM controller
DMA controller
Parallel interface controller
Video output port
LED STB output port
Timer
I/O Port
A/D converter
(2) Program ROM
Program ROM contains a program for the equipment. EPROM is used as program ROM. When mask
ROM in the one-chip CPU explained in (1) above is valid, the EPROM is not mounted. (For details on
short wiring setting, see Section 7.2.)
(3) DRAM
DRAM is used as resident memory.
(4) EEPROM
EEPROM holds the following data:
l Menu data
l Counter value
l Adjustment value
Service Manual for OKIPAGE 8z
Chapter 2 Operation Description
Function
Controls DRAM.
Transfers image data from Parallel I/F to DRAM, from
DRAM to a video output port and between CPU and
DRAM.
Controls the parallel interface.
Controls LED head.
Generates various control timings for monitoring paper
feeding and a paper size.
Inputs and outputs the sensor signals and motor
signals, etc. Also performs I/O for EEPROM.
Inputs the feedback signals from a high-voltage
generation circuit and thermistor signal.
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