Service manual

EPSON Stylus Photo 870/1270 Revision B
OPERATING PRINCIPLES Electrical Circuit Operating Principles 46
2.2.2 C304MAIN Board Circuit Operation Principles
The C304MAIN board includes the following:
!
Logic circuit (CPU, ASIC, DRAM, EEPROM, and so on)
!
Various motor control/driver circuits (CR motor, PF motor, and
ASF/Pump motor)
!
Head control/driver circuits
!
Interface circuit (parallel I/F, USB I/F)
!
Sensor circuit
!
Timer circuit
!
Reset circuit
The C304MAIN board is mainly different from other main boards in the
following two points.
1) Use of 3.3V drive logic chips
IC9, the 3.3 V regulator IC on the C304MAIN, produces 3.3 V by
pressuring down the 5.5 VDC generated on the C298PSB/PSE board to
drive several chips. These chips are used to reduce power used to
drive the logic circuit. See the table below that separately shows the
chips driven by the +5V and +3V.
Table 2-8. 3.3V Drive Chips & 5.5V Drive Chips
2) Use of slave CPU
Since the CR motor and PF motor of this printer are DC motors, a
slave CPU is attached on the main board in addition to the CPU and
ASIC. This slave CPU exclusively controls the DC motors to remove
the task from the CPU and ASIC. So the CPU and ASIC can process
data faster than before.
See Figure 2-12 for the C304MAIN board block diagram.
Figure 2-12. Block Diagram for the C304MAIN Board
+5V 3.3V
Sensors
I/F Circuit
PNL Board
CPU
ASIC
P-ROM
D-RAM
C90A11CA
CPU (IC20)
Address
Data
Address
Data
CR1
Timer &
Reset IC
(IC5)
Batt1
EEPROM
(IC6)
CN1 Parallel
Common
Driver
(IC10 or
IC11)
Q3&Q4
CN8 HD FFC
Motor
Driver
(IC18)
Motor
Driver
(IC19)
PF Motor
CR Motor
CN14
CN13
C304PNL Board
CN11
CN 6
ASF Sensor
CN5
PE Sensor
E05B70CD
ASIC (IC8)
D-RAM 16M
(IC3)
CN9 HD FFC
C90A26CA
Slave CPU (IC15)
CN7
Motor
Driver
(IC12)
ASF/Pump Motor
P-ROM 16M
(IC2)
CN7
PF Encoder Sensor
Head
CR Encoder senser
IC4
74VHC1612B4
CN3
USB
IC7
IC21
E0BA13KA
PDIUSBF11A