Epson 2180 - LQ B/W Dot-matrix Printer, Service Manual

Page: 29 / 56

LQ-2180 Revision A
Operating Principles Control Circuit 29
2.1.6 EEPROM Control Circuit
When the printer power is turned off, the EEPROM stores the factory
settings and values in the areas that are not cleared in the user setting
mode and also writes those values in the RAM. This sequence is
managed by the CPU (IC4), which transmits data in the serial format.
The EEPROM control circuit is as shown below:
2.1.7 Sensor Circuit
Unlike the LQ-2170, both the CPU and the gate array monitor and
control the corresponding sensors’ conditions. Note analog voltages are
all monitored by the CPU ports.
Figure 2-8. Sensor Circuit
C P U ( I C 4 )
9
1 0
1 1
1 2
A T 9 3 C 4 6 ( I C 5 )
P 7 0
P 7 1
P 7 2
P 7 3
C S
S K
D I
D O
1
2
3
4
C P U ( I C 4 )
P 3 6
P 4 0
A N 2
P 5 3
P G S e n s o r
R e l e a s e
S e n s o r 1
R e l e a s e
S e n s o r 2
+ 5 V
+ 5 V
H P S e n s o r
+ 5 V
+ 5 V
R e a r P E
S e n s o r
+ 5 V
F r o n t P E
S e n s o r
+ 5 V
+ 5 V
P W , T O P
S e n s o r
C o v e r O p e n
S e n s o r
1 8
7 6
7 5
6 8
7 0
G A ( I C 3 )
R e l e a s e 1
R e l e a s e 2
1 1 6
1 1 7
6 1
P 2 7
I N T 7
Figure 2-7. EEPROM Control Circuit