2.3.2 System Reset Circuit
Control circuits IC1 and IC2 are initialized when a RESET signal (LOW level) is output from port 1 (VOUT)
of IC10.IC10 monitors the+5 V line on port 3, andresets under thefollowing condi tions:
1. When the powersupply is turned on, a RESETsignal is output.RESET is canceledwhen the
+5V line goesup to 4.2 V, andthen 100 ms passes.
2. When the +5 V linegoes below+4.2 V, a RESETsignal is output.RESET is canceled when the
+5 V linegoes back up to4.2 V and then100 ms passes.
2.3.3 Printhead Driver Circuit
Thestandard voltage for theA/D converter ismade in ZD1 andinput toCPU port 78. Based on this standard
voltage, theA/D converter inthe CPU operates. Port 74 monitors the +35 V linebetween R50 andR51 to
determine theprinthead drive pulse width.Using the monitored voltage,the CPU converts the voltageto a
digital value and decides theprinthead drivepulse width, andthen transports the data to thegate arrayvia
CPU port 19. Basedon the monitored voltage,the CPU decides the printing interval. Port 73monitors the
printhead temperature to protect theprinthead. If the temperature exceeds 107°C (225° F) , printingis
stopped.
CPU
Gate
Array
C19
ZD1
+35V
7879
74
73
R51
R50
+35V
R49
Address
Data Line
37
44
~
28
~
21
Printhead Drive Signal
69 76~89 91~93
Printhead Drive Transist or Q 5~Q13, Q14~ 22
Print Head
HTMP
+
C9
+35V +35V
32 19
Figure 2-34 Printhead DriverCircuit
VOUT
MRES
VCC
GND
+5V
+5V
R47
1K
IC10
PST5920
C16
0.1U
IC1
IC2
E05813YA
TPM96C041AF
23 RESET
61
RESET
1
2
3
4
Figure 2-32 Reset Circuit
1
2
3
4
5
VCC (+5V line)
VOUT (RESET)
RESET RESET
Power On
(v)
100ms 100ms
Figure 2-33 Reset SignalOutput Timing
Operating Principles FX-2170 ServiceManual
2-24 Rev.A