Control Circuitry - Epson TM U200D - B/W Dot-matrix Printer Technical Manual

+5V DC control circuit
The +5V regulator circuit switches the +24V power input and converts it to +5V. The switching
regulator IC (U1) switches the +24V input, smooths it via C1, and outputs +5V. Power for the
RS-232 is generated by the internal charge-up circuit on the RS-232 interface driver.
U5
30 WDTOUT
P80 WDTOUT
73 +24COM SW
P51/T04
74 CRCOM SW
P52/T05
76 PFCOM SW
P53/INT1/TI4
CN1
F1
1
+30V 1
2
GND 2
3
N . C 3
4
F . G SH
F . G

Control Circuitry

Reset circuit
The reset circuit is used to prevent the CPU from operating erratically and the print head from
printing unexpectedly during the period of unstable voltage immediately after the power is
turned on. To accomplish this, the OUT terminal output (pin5) of the reset IC (U9) is supplied to
the CPU (U5) as the -RESET input signal (pin 21).
The reset IC (U9) monitors the +5V voltage. When the voltage is 4.5V or more, the reset is
released for the CPU and other components, and the printer becomes ready.
In addition, the C terminal (pin 4) of the reset IC (U9) is connected to the reset signal (DSR signal
or pin 25 input signal) from the host interface via DIP switches 2-3 and 2-4. If a reset signal is
applied to this pin, the reset IC output goes low and the CPU and other components are reset.
The reset signals differ depending on the interface specifications:
Rev. B
+5V
Q27
Q24
R59
Q1
G
N
D
Q2
Q3
D6
+24DT
C12 C11
R17
L1
P.G
GND
R9
1M
FG GND
C13
Figure 2-18 Power supply circuit diagram
TM-U200D/U200PD Technical Manual
D4
R5
G
N
U2
D
+24DT 5
VIN
D47
2
SW
+
R6
C14
_
D48
D3
R7
U3
5
VIN
G
2
D49
N
SW
D
GND
+
D5
C10
_
U4
5
VIN
G
2
N
SW
D
GND
SW1 R42
+5I 1 2
Power switch
C2
Mechanism Configuration and Operating Principles
+24A
HEAD COM
3
VOUT
A / C COM
DKD COM
4
SEN
+ +
C45 C16
_ _
1
GND
3 +24B
VOUT
CR COM
4
SEN
+
C6 C7
1 _
3 +24C
VOUT
PF COM
4
SEN
+
C8
C9
1 _
{5 V
1
U1
10 1
IN OUT
6
LIN
+ + +
G
_ _ _
C3 5
C1 C5
GND
C41
GND
1