OKIDATA ML393C Plus, Руководство по обслуживанию

Страница: 43 / 323

Page: 34
Service Guide ML393/ML393CPlus
Chapter 2 Principles of Operation
2.1.02 Microprocessors (MPUs) and Peripheral Circuits
Microprocessors (Q16: 83C154UGS and Q11: 80C154VGS)
The Microprocessors are the nucleus of the control circuit. The peripheral circuits operate under program
control by these microprocessors. The Master MPU (Q16) controls the interface, code processing and the
Slave MPU. The Slave MPU (Q11) controls the spacing and printing functions.
Program ROM for Master MPU (Q6: 27512)
This Program ROM contains the control program for the printer. The master microprocessor operates by
execution of this program.
Program ROM for Slave MPU (Q17: 2764)
This Program ROM contains the control program for the printer. The slave microprocessor operates by
execution of this program.
DRAM (Q18 and Q19)
The Dynamic RAM chips, each consisting of 64x4 Kbits, are used as the Receive Buffer and Print Buffer.
The total buffer size is 64x8 Kbits.
CGROM (Q7)
This is a 1 Mbit ROM which stores the resident character fonts.
EEPROM (Q20)
This 256-bit serial Electrically Erasable and Programmable ROM stores the menu data.
Motor Control LSI (Q9: MSM6990)
This LSI controls the functions listed below.
Space Motor Speed Control
To obtain the carriage speed instructed by the Microprocessor, the LSI generates the pulse switch timing
and overdrive time
Dot ON Timing generation
I/O Port (Input port used to read Operator Panel switches)
Address Latch (for lower 8 bits of the slave MPU)
LSI (Q8: MSM74H002)
This LSI drives the 24 pin printhead. The following describes the function of the LSI.
Printhead Drive Control
Printhead Drive Correction
Modifies the drive time under the following circumstances
Correction for edge pin driving
Correction for drive voltage fluctuations