Oki 4M, 4W PLUS specifications Main Control Board, Eeprom

2.1Main 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 a 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, 10-MHz clock) incorporating mask ROM and CPU peripheral devices. This CPU has the functions listed in the table below.

Built-in Device	Function
DRAM controller	Controls DRAM.
DMA controller	Transfers image data from Parallel I/F to DRAM, from DRAM to a video output port and
	between CPU and DRAM.
Parallel interface controller	Controls the parallel interface.
Video output port	Controls LED head.
LED STB output port
Timer	Generates various control timings for monitoring paper feeding and a paper size.
I/O port	Inputs and outputs the sensor signals and motor signals, etc.
	Also performs I/O for EEPROM.
A/D converter	Inputs the feedback signals from a high-voltage generation circuit and thermistor signal.

(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:

•Menu data

•Counter value

•Adjustment value

(5)Parallel interface

The parallel interface receives parallel data from the host; it conforms to the IEEE1284 specification.

(6)Macintosh interface <only OKIPAGE 4m>

Mcintosh interfacce receives serial data from the host ; it conforms to the IEEE1284.

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