Service manual

EPSON Stylus Photo 870/1270 Revision B

OPERATING PRINCIPLES Electrical Circuit Operating Principles 47

Table 2-9 shows the major ICs on the C304MAIN Board and their functions.

Table 2-9. Major Element on C304MAIN

IC Location Functions

CPU (C90A11CA) IC20

A 128-pin SQFP package. Operates at 24.0MHz. Power supply

voltage is 3.3V.

• Sets the current value for the ASF/Pump motor.

• Measures the printhead temperature.

• Several interrupting functions

• Outputs the system clock signal.

ASIC (E05B70**) IC8

A 240-pin QFP package. Operates at 48.0MHz/24.0MHz/28.0MHz.

Power supply voltage is 3.3V.

• Controls interfaces.

• Controls specified motors.

• Controls the printhead drive waveform circuit.

• Transfers serial data to the printhead.

• Controls the ASF/Pump motor

• Receives panel control signals and sensor signals

• EEPROM

• Controls detection of the signals output from the encoder.

Slave CPU

(C90A26CA)

IC15

A 128-pin SQFP package. Operates at 24.0MHz. Power supply

voltage is 3.3V.

• Controls the DC motors. (Setting and controlling the current

value for the PF motor and CR motor)

PROM IC2

8/16Mbit

• Stores the firmware or firmware +CG

DRAM IC3

A 16Mbit DRAM. Power supply voltage is 3.3V.

• Serves as specified buffers and work area

EEPROM

AT93C56

IC6

2kbit

• Stores default setting values and specified parameters.

Reset IC

RTC9810SA

IC5

• Resets the +5V/+24 VDC line circuits.