Sensor Circuits - Epson LQ-870 Service Manual

REV.-A
VCCON
DISC
THLD
RESET

2.3.3 Sensor Circuits

Figure 2-21 shows the sensor circuits in block diagram form. When the printhead temperature exceeds
the maximum allowed value, the TEMP2 signal and other signals, such as the CRHOME signal, are sent
directly to the CPU. The +35 V line signal passes through the reset circuit before it reaches the CPU.
Terminals P50 to P55 in the CPU are used for the A/D converter. The Vref circuit generates the A/D
converter reference voltage Vref.
C P U (1C)
Power On
Figure 2-20. /RESET Signal Timing
P31
NMI
4 . 7 4 1 v
V r e f -
Figure 2-21. Sensor Circuit Block Diagram
CPU Self Reset
RESET
P S T 5 2 9 C (36)
V r e f C i r c u i t
2 - 1 8
L E V E R 3 1
T 2 8