Gp 16 Engine Controller - Xerox WorkCentre M20 Service Manual

Figure 1 USB interface
Features
• USB Specification Version 2.0 Compliant (high and full speed).
• Interfaces between a local CPU bus and a USB bus.
• Supports USB Full Speed (12 Mbps) and High Speed (480 Mbps).
• Supports optional Split Bus DMA, with dedicated DMA and CPU access.
• Provides 3 Configurable Physical Endpoints, in addition to Endpoint 0.
• Provides 30 Configurable Virtual Endpoints.
• Each endpoint can be lsochronous, Bulk, or Interrupt, as well as IN or OUT.
• Supports high-bandwidth isochronous mode.
• Supports Max Packet Size up to 1K bytes, double buffered.
• Internal 3 Kbyte memory provides transmit and receive buffers.
• Local CPU bus easily interfaces to generic CPUs.
• 8-bit or 16-bit CPU or DMA bus transfers.
• Multiple register address modes supports both direct and indirect register addressing.
• Automatic retry of failed packets.
• Diagnostic register allows forced USB errors.
• Software controlled disconnect allows re-enumeration.
• Atomic operation to set and clear status bits, simplifying software.
• Low power CMOS in 64 Pin Plastic TQFP Package.
• 30 MHz oscillator with internal phase-lock loop multiplier.
• Provides an output clock to the local bus-8 programmable frequencies from OFF to 60
MHz.
• 2.5V, 3.3V operating voltages with 5V tolerant I/O.
Work Centre M20 Family

GP 16 Engine Controller

Purpose
To give information about the machines control circuits:
• Fuser Control/Thermistor Circuit
• Paper Sensing Circuit
• LSU Circuit
• Fan/Solenoid Actuation Circuit
• PTL Actuation Circuit
• Motor Actuation Circuit
• High Voltage Power Supply
NOTE: If necessary, refer to GP 20 for the acronym list and cross reference lists of more com-
monly recognised part names.
Fuser Control/Thermistor Circuit
This circuit controls the heat lamp temperature to fix the transferred toner onto the paper. It is
comprised of the thermistor that has the negative
LM393 (voltage comparator) and transistor for switching.
The thermistor has the resistance value reverse proportional to the heat lamp surface temper-
ature. The voltage value is read by #60 pin(AVIN2) of CPU referring to the parallel combined
resistance with the resistor(R43) connected parallel to it and the voltage distribution of R29.
The voltage read activates (inactivates) 'fuser' signal to high (or low) referring to the set tem-
perature and when the 'fuser on' signal turns down (high) to low (high) by Q3 switching, the
S21ME4 inside SMPS (PC3) turns on (off) and this eventually turns two-way thyristor (SY1) on
(off) to allow (shut) AC voltage to the heat lamp.
LM393 is a H/W designed to protect the system when the software heat lamp control does not
run normal. When the thermistor temperature goes up to 210C, #1 pin's level (LM393) will turn
low to turn the 'fuser on' signal to high. (forcefully shuts off Q3)In other words LM393 shuts off
the heat lamp forcefully.
Paper Sensing Circuit
Cover Open Sensing
Cover Open Sensor is located on the right rear side of the printer. In case the right cover is
open, it shuts +5V (LSU laser unit) and +24V(main motor, polygon motor of fixer LSU and
HVPS) that are supplied to each unit. It detects the cover opening through CPU. In this
case, the red LED of the OP Panel LED will turn on.
Paper Empty Sensing
The paper empty sensor (photo interrupter), located inside bottom of the bin cassette detects
paper with the actuator connected to it and informs the CPU of whether there is paper. When
there is no paper in the cassette, the red LED of the OP panel LED will turn on to tell the user
to fill the cassette with papers.
March 2004
6-27
resistance against the temperature and
General Procedures and Information
GP 15, GP 16