Operation Description; Main Control Board - OKIDATA OL810e Service Manual

2.1 Main Control Board

The main control board consists of a single chip CPU, a program ROM, a font ROM, four DRAMs, an
EEPROM, a host interface circuit, and a mechanism driving circuit.
(1) Single chip CPU
The single chip CPU is a custom CPU (32-bit internal bus, 32-bit external bus, 25.54-MHz clock, with input
frequency from a 12.27-MHz clock) which incorporates the RISC CPU and its peripheral devices, and has
the following functions:
Built-in device
Chip select controller Control of ROM,
DRAM controller
DMA controller
Parallel interface controller
Serial interface controller
Video output port
LED STB output port
Timer
Serial I/O port
I/O port
(2) Program and Font ROMs
The Program and Font ROMs store the equipment program and various types of fonts. EPROM or Mask
ROM is used as Program and Font ROMs. The mounting locations of these Program and Font ROMs vary
depending on the type of the ROMs (for the mounting location see Section 7.4).
(3) DRAM
The DRAM is a 2MB resident memory which is used as a buffer, that stores edited data, image data, DLL
data and macro data.
(4) EEPROM
1,024-bit Electrically Erasable PROM (EEPROM), is loaded with the following kinds of data:
Service Guide OL810e
Chapter 2 Operation Description
Function
DRAM and I/O device Bus controller
Transfer of image data from DRAM to video output port
Control of Centronics parallel interface
Control of RS-232C serial interface
Control of LED head
Generation of various control timing
Monitoring of paper running and paper size
Control of operator panel, EEPROM, and options
Input and output of sensor and motor signals
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