Reset Circuit - Epson FX-870 Service Manual

Reset Circuit

The control circuits are initialized when the RESET signal is issued. The reset operation occurs
under these two conditions:
1. Power on reset
Immediately after the power is turned on, +35 VDC is rapidly generated. Because it takes a
moment for the voltage at ZD2 to reach +31.5 V, the voltage at the DISC terminal on the gate
array does not reach +5 VDC until capacitor C24 is fully charged. A similar integration circuit
is provided in the gate array and further delays the output of the ROUT signal. This LOW
level is used as a reset signal.
2. INIT signal reset
The reset signal is also issued when the INIT signal is sent from the host computer.
Figure 6-25 shows the power on reset circuit.
Epson FX-870/1170
DISC ROUT
RIN
Principles of Operation
I 15
6-25