Epson LQ-670 - EEPROM Control Circuit; System Reset Circuit

Chapter 2 Operating Principles
Rev. A
2-1
4
2.2.2.2 EEPROM Control Circuit
EEPROM(IC9) uses three lines serial in/output 1kbit EEPROM and records default setting values and
destination parameter. Control signals of EEPROM; CS,CK,DO, DI are attached in the CPU port P70∼73
and, are controlled. When the power off is detected, the CPU writes the necessary data to the EEPROM
before the +5V line drops out of the normal range. The other CPU access is done during power supply,
but the access for safety is not done when the CPU is in the reset state.
2.2.2.3 System Reset Circuit
The reset IC(IC12) of this printer sends reset signal to the CPU and gate array until +5V line for control
stabilizes after the power is turned on, and prevents the printer from going to mis-operation.
EEPROM
(IC9)
Power-off
CS
CK
DI
DO
CPU
(IC11)
INTO
P70
P71
P72
P73
Figure 2-10. EEPROM Circuit
ResetIC
(IC12)
+5V
/RESET
VOUT
/RESET
MRES
P26
Gate Array
(IC10)
CPU
(IC11)
Figure 2-11. Reset Circuit