User's Manual

33
TTP-248M Bar Code Printer
Service Manual
2. Selecting AUTO RIBBON to detect ribbon will get a value of tension, and then
selecting the MANUAL Ribbon.
When sensor detects ribbon:
LCD displays Not Through  the voltage of receiver (PIN 4)≦1.26V
When sensor detects no ribbon:
LCD displays Through  the voltage of receiver (PIN 4)≧2.10V.
GND
VCC
8 9
U4D
74HC14
R9
10K
R77
100
REND_SENS
R_END
1
2
3
4
5
JP22
R_SENS
Fig. 3.14 Ribbon End Sensor Circuit
3.12 Serial Port Circuit
C1+
1
V+
2
C1-
3
C2+
4
C2-
5
V-
6
T2OUT
7
R2IN
8
R2OUT
9
T2IN
10
T1IN
11
R1OUT
12
R1IN
13
T1OUT
14
VCC
16
GND
15
U31
SP3232 E
C9
0.1u
C10
0.1u
VCC
C11
0.1u
C17
0.1u
GND
GND
L7
BEAD 300
L8
BEAD 300
L9
BEAD 300
L10
BEAD 300
C12
0.1uGND
F1
1A
TX
RX
DSR
RDY
GND
5
9
4
8
3
7
2
6
1
JP3
DB9_1
VDD
VCC
1
RxD
2
TxD
3
GND
4
D+
5
D-
6
R-
7
R+
8
U32
LTC490
GND
VCC
R80
120
R81
120
L13
INDUCTOR1
L14
INDUCTOR1
L15
INDUCTOR1
1
2
JP28
2PIN
L12
INDUCTOR1
U1/168
U1/174
U1/176
U1/170
RxD2/SCPT4
TxD2 /SCPT4
CTS2/IRQ5/SCPT7
RTS2/SCPT6
Fig. 3.15 Serial Port Circuit
U18 (SP3232E) is RS232 asynchronous communication driver IC.