OKIDATA DOC-IT3000, Service Manual

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Service Guide DOC-IT3000/4000
Chapter 2 Principles of Operation
2.2.02 Printer Control Board
The Printer Control Board is composed of an MPU80C154, MSM75V039, ROM and EEPROM.
· MPU80C154
- 8-bit CPU
- Internal RAM: 128 bytes
- I/O ports: 32
- Internal ROM: 8K bytes (not used)
- Interrupt lines: 5
· EEPROM
- 8-kbit electrically erasable PROM (EEPROM), which is loaded with the following kinds of
data:
- Total number of sheets printed after installation/Total modified number of sheets printed
after installation
- Total number of sheets printed with the drum currently in use
- Total number of sheets printed with the fuser currently in use
- Setting of time required from completion of print to stand by
- Feed length needed to feed the paper to a printable position
- Print starting line on paper (Top margin)
- Time needed to turn on LEDs in the LED head
- Error log number
- Feed length needed to feed the paper to a readable position (ADF)
- Total number of sheets scanned with ADF
- Total number of sheets fed with ADF currently in use
- Slip correction values of document sheets on the ADF
· MSM75V039 (80 pin LSI)
- Data transfer to the LED head
- Address latch & address output
- 8 bit interface
- LSYNC cycle set counter
- Serial interface
- EPROM (contains the printer control program)
· Printer control gate array (MSM75V039)
- Frequency divider circuit
- A 1/6-frequency divided signal with the oscillator (11.059 MHz) connected to the external
source is used as a system clock inside the gate array.
- Strobe pulse set circuit
- The strobe pulse set circuit has a strobe width register and can be set freely.
- The strobe width register sets the pulse width of a strobe signal that is output to the LED
head.
- The pulse width of the strobe signal is usually set when the power of the Doc-It Engine is
turned on and when the vertical resolution setting is altered.
- Setting range: 1.084 ns to 2.33 ms