Reset Circuit - Epson LQ-1170 Service Manual

2.3.2 Reset Circuit

Figure 2-19 shows the reset circuit in block diagram form. The reset circuit issues the /RESET signal.
The control circuits are initialized when they receive the \RESET signal. The conditions under which
the \RESET signal is output are described below.
When you turn on the power
Immediately after you turn on the power, PST-520 (6C) outputs the /VCCON pulse. E05A49 (46) receives
this pulse and outputs the /DISC pulse. Then the electrical charge through the resistor (R49) in the
condenser (C28,C29) is discharged. After this, E05A49 outputs the THLD signal and E05A49 outputs
the /RESET signal. After a certain time has elapsed, the charge in the condenser builds up again. The
When the CPU performs a reset (CPU self-reset)
The CPU outputs the /RESET signal if there is a /RESET request for E05A49 and if E05A49 has output
the /DISC pulse.
- - - - - - - - - - -
Line
PST520
1
3 9
OUT
R69 2K
11
Figure 2-19.
(4B)
- - - - - - - - - - - -
DISC
Reset Circuit Block Diagram
2 - 1 7
CPU RSET 22 PIN
OPTION RST 1 I PIN