Power On Reset'circuit; Power Offsensorcircuit - Epson LQ-300 Service Manual

Manual
Power On Reset Circuit
2.3.2
When the power supply is turned on and immediately the VL (+9 V) goes up to +7.5 V (typical), the
reset IC (IC6) outputs the system RESET signal (LOW). The CPU and gate array receive this LOW
level signal from the reset IC and reset themselves.
GATE ARRAY
2.3.3 Power Off Sensor Circuit
When the power supply is turned off and the VP (+35V) immediately goes down to +25 V (typical),
the reset IC (IC7) outputs the system RFSETsignal (LOW). The CPUreceives this LOW Ievelsignal
from the reset IC and resets itself.
Figure 2-14. Power Off Sensor Circuit Diagram
67
XRST
2
IN
4
+5
Power Off
Sensor IC (IC7)
15
1
Operating Principles
16
RESET
CPU
L
(ICI)
O U T 6
VP
2
I
2-13