Service manual
+5V
CIRCUIT
THEORY
U5D
6532
U6D
6522
PA6
14
iii
c:
'"
u;
8
....:
iii
CAt
40
-
c:
s-
I/)
a:
CA2
1=-39~-J
TIMING CHART
*TIMING SIGNAL
U1C-9
PIN
U1C-8
PIN
(PA6)
Rl0
47 k
U1C
9
U1C
Rll
Pl
Jl
47 k
R9
150 n
12
12
19
19
,.,
CARRIAGE POSITION SENSOR
20
20
"'"
HOME
POSITION SENSOR
~~--~--~t5
t5~----~----~
--------lnn
_______
__
U U L
)I " APPROX.
1.5
ms
inn
n n n rr - - - -
--
-
-n
n
u u u u U U L
_______
--.J
U L
PLACE MAGNET CURRENT
FLOW OPENING POSITION
PLATE MAGNET
CURRENT FLOW
OPENING POSITION
FOR
THE NEXT
LINE.
*RESET SIGNAL
1\
-=U~1C~-~1~1~P~IN~
____________________________
~)
~~
____
_
U1C-10
PIN
(PA7)
WHEN CARRIAGE HAS
RETURNED TO ITS
HOME POSITION
PRINT STOP
SIGNAl)
Position
Sensor
and
Home
Sensor
Circuit
Theory
PRINT START
SIGNAL
FOR
NEXT
LINE
PRINT
When printing,
the
print
head moves across
the
paper on
the
carriage assembly. The carriage assembly
is driven
by
a carriage stepper
motor.
As
the
stepper
motor
turns,
a
photo-coupler
device generates
"low"
pulses
which
are
input
to
U 1 C pin
9.
U 1 C is
an
inverter. U 1 C generates
"high"
active
pulses
which
are
input
at
U5D pin
14
(PA6), and
U6D
pin
40
(CA 1). A
subroutine
in
the
operating
system
monitors
the
pulses generated
by
the
photo-coupler, providing processor controlled
print
head posi-
tioning.
A second
photo-coupler
device provides a synchronizing pulse or a
start
pulse
when
the
print
head is
at
the
far
left
(Home) position. The
output
of
the
photo-coupler
is
input
to
U 1 C pin
11.
The
output
on pin
10
is
input
at
U5D pin
15
(PA5) and U6D pin
39
(CA2).
16