Microprocessor (Mpu) And Peripheral Circuits - OKIDATA Pacemark 3410 Service Manual

Page: 15
Service Guide PM3410
Chapter 2 Principles of Operation

2.1.02 Microprocessor (MPU) and Peripheral Circuits

Microprocessor
Q3: M67X640V1
The MicroProcessor Unit (MPU) is the nucleus of the control circuit. Various peripheral circuits operate
under program control of this microprocessor. The MPU (Q3) controls all aspects of printer operation.
Program ROM for the MPU
Q4: 27C202K
This 2Mbit Read Only Memory (ROM) contains the control program for the printer. The MPU operates
under program control.
This ROM also stores the resident character fonts.
DRAM
Q10 and Q11
The Dynamic Random Access Memory (RAM) chips, each consisting of 64 K x 4 bits, are used as the
Command Buffer, Receive Buffer and Print Buffer.
The total buffer size is 64 K x 8 bits. The RAM speed is 120 ns.
EEPROM
Q14: 93C06N
This 256-bit serial Electrically Erasable and Programmable Read Only Memory (EEPROM) stores the
menu data and initial settings for the LSI circuits.
Interface/Motor Control LSI
Q5: B562 13497
This LSI controls the following functions listed below.
Space Motor Enable / Speed Control
To obtain the carriage speed instructed by the microprocessor, Q5 uses the signals SP - Phase A and SP
- Phase B, derived from space motor movement to generate the pulse width timing and overdrive time.
Line Feed Motor Phasing Control
To turn the line feed motor in the proper direction, this LSI sends motor drive signals (properly phased) to
the line feed driver (TRA4).
Bail Motor Phasing Control
To turn the bail motor in the proper direction, this LSI sends motor drive signals (properly phased) to the
bail driver (TRA3).
Dot ON Timing signal generation
Q5 uses the signals SP - Phase A and SP - Phase B, derived from space motor movement, to produce
the signal IPT. This signal (IPT) is used to enable the print wires at the desired carriage position.
Printhead / Bottom Tractor Feed Control LSI