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7. Printer control circuit
1) Paper feed motor circuit
A pulse motor is used as the paper feed motor.
Drive sequence of the pulse motor is as follows:
SEQUENCE
SIGNAL
A
/A
B
/B
STEP1
High
Low
Low
High
STEP2
High
Low
High
Low
STEP3
Low
High
High
Low
STEP4
Low
High
Low
High
2) Print circuit
Thermal head configuration
As shown in the equivalent circuit in the figure, thermal head con-
sists of heating elements and head drivers which drives and con-
trols those heating elements.
The serial print data input through the DATA IN (D1) is transferred
to the shift register synchronizing with the CLOCK (CP) and stored
to the shift register synchronizing with the CLOCK (CP) and stored
in the latch register by the LATCH (LA) signal.
The head conduction signals (print commands 1 ~ 6) turn the gate
on to conduct the heating element corresponding to the print data.
Equivalent circuit of thermal head
Head splitting
The thermal head has 6 strobes so that it is possible to print
dividing up to 6 times. The relationship between the strobes and
dividing up to 6 times. The relationship between the strobes and
heating elements is shown below.
Strobe terminals and conduction heating elements
STB No.
Heating element No.
Number of dots/STB
1
1 ~ 64
64
2
65 ~ 128
64
3
129 ~ 192
64
4
193 ~ 256
64
5
257 ~ 320
64
6
321 ~ 384
64
Print data and printing position
384-bit data No.1 ~ 384 transferred by the DTA IN (DI) are printed
in the position shown in the figure.
CPU
74HC32
VH-
VH-
/A
A
B
PH1
PH3
PH2
PH4
/B
To Papper feed motor
LB1843V
74HC123D
LB1843V
STB6
23
VH
1,2,3,26,27,28 dot 384
L-GND
18
P-GND
13,14,15,16,17
STB5
22
STB4
21
STB3
10
STB2
9
STB1
8
/LATCH
5
DATA IN
25
CLOCK
6
DATA OUT
4
VDD
7
NC
19,20,21
TM
11
TM
12
dot 1
6
5
4
3
2
1
Heating element
Latch register
Shift register
Thermister
STB terminal is pulled down inside the IC.
DATA IN
1 2 3 4 ..........................383 384
Paper feed direction
Record paper
Print surface
Data
Printer mechanism
Motor
Print data and printing position
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