Commodore 1515 Technical Manual page 17

(2) Start of the printing motions
MOTOR
(pg/S")
I
--f
about-----------------------------------------
160 ms
t--
He (P8/9)
I
[
HOME (PI/IZ)
First dQt of Fiest dot
of
dot position 0 dot position 1
j4-- 5.56
ms---l
--..,;---......
~
.. 2
3
4 5
6 7 1 2 3 4
~OT
(P3/8)
nnnnnnn
nn
_ _ _
---<5fj~uuuu~~:
: : : .. : : :
PI N
(~P-S~/J-3 ~)
- - - 580
Il
S 1.9 ms
----t'=t~~~~~
Figure
13
First column
of pattern "A"
\-
. .
Second
column
When printing starts, the CPU makes the MOT (P8/S) andHC signal
LOW. Lowering of the MOT signal makes the drivers (P7/l5,16) LOW supplying current
to the motor to race. Since the
H
C signal is also LOW. 'the H solenoid is activated
to relieve the motor shaft from the head carrier for about .160 ms so that the .ator
can reach constant speed of revolution. TheFfC signal is raised to HIGH engaging
the motor shaft and the head carrier to move it to the rightward direction. In case
there is no or abnormal output from the dot sensor, the CPU turns theHC and lUYr
signals HIGH and halts to do nothing because aechanical error must have occurred.
Next, the CPU waits and sees if tho printhead leaves the home position via the
HOME signal (Pl/12). After confirming that the HOME signal becomes LOW which means
the head carrier gets out of the home
positi~."
the CPU goes to check the DOT signal
(P3/8) in order to decide when to start printing. The DOT signal is a shaped output
signal of the dot sensor and a group of 27 seruential pulses repeats at a constant
interval. The rising edge of the DOT signal following the comparatively long duration
of staying LOW (1.9 ms) is the timing to start printing. When this signal rises from
LOW to HIGH after staying LOW for .are than
640~s,
the CPU takes it as a'timing to
start printing and jumps to the hammer drive routine. In case of printing one dot,
the
~lN
signal (PB/13) of the hammer drive pulse which is synchronized with the DOT
signal is made LOW for about 290;Ms. Lowering of
t~e
PIN signal . . kes the driver
(P7/IO) LOW, turns the transistor (Ql) ON and drives the hammer. The 27 pulses
consist of three 7-dot columns as shown below.
15