Microprocessor And The Peripheral Circuit - OKIDATA ML320 Turbo Service Manual

Page: 5
Service Guide ML320/321Turbo
Chapter 2 Operation Description

2.1.2 Microprocessor and the Peripheral Circuit

(1) Microprocessor (Q7: 67X640)
This processor is a CMOS single-chip computer with integrated peripheral device functions and a 16-bit
MPU core, all OKI original architecture.
The processor has a 20-bit address bus and a 16-bit data bus.
It is capable of accessing up to 1M word program memory and 1M bytes of data memory.
The following characteristics are also provided:
- Built-in type data memory of 512 bytes
- 8-bit 4-channel A/D converter x 1
- 16-bit automatic reload timer x 2
- 8-bit serial port x 2
- 8-bit parallel port 3 3 (bitwise I/O specification available)
And others.
The function of this microprocessor is to provide a central mechanism for the entire printer by executing
the control program through the LSI and driver circuits.
(2) Program ROM
This is a 256 x 16 bits (4M bit) [MAX] EPROM with the control program for the printer stored. The MPU
executes instructions under this program.
The program ROM is assigned to the program memory area of the MPU and is fetched by the PSEN
signal of the MPU.
The following shows the operation of the memory access.