Commodore MPS-801 - PREPARING TO USE YOUR PRINTER; Installing and Removing the Ribbon Cassette

2. Start of the Printing Operation
When printing starts, the CPU sets the MOT signal (P5/30) and the HC signal (P5/29) LOW. When
the MOT signal goes LOW, the driver GP-DR-2/1 0 goes LOW (ON) causing the motor to rotate. Since
the He" signal is LOW, the H solenoid is activated, which disengages the motor shaft from the print
head carrier so that the motor can reach a constant speed before any movement of the print head
occurs. After approximately 160 ms, the HC signal is set HIGH, which causes the motor shaft and
the print head carrier to engage, and allows the print head to be driven to the right. Next, the CPU
waits to see if the print head leaves the home position by sampling the HOME signal. After confirming
that the HOME signal has gone LOW, which means the print head carrier has moved out of the home
position, the CPU checks the DOT signal in order to decide when to start printing. The DOT signal
is a shaped
output signal from the dot sensor and, as shown in the figure below, it comes in groups
of 34 sequential pulses. When the HOME signal goes LOW, the CPU starts to count the number of
dot pulses until the DOT signal stays HIGH for approximately 0.9ms. The CPU then compares this
number with the number stored during initialization in order to decide when to start printing.
MOT (P5/30)
He (P5/29)
-=1
160
msf=
HOME (TEST PIN)
II
0.9 ms
DOT (TEST PIN)
III
11111· ...... ul~
mill u ... u.u .. uu·111
32 34
135
32 34
3 5
32 34
3. Printing Operation
The CPU synchronizes the PIN signal (P5/27) to the DOT signal. The PIN signal is for driving the print
hammer; when it goes LOW, the driver (GP-DR-2/1) goes LOW (ON) to activate a print hammer to
print a dot.
.-------- 11.9 ms----------
-"'---"-T- 0.9 ms
DOT
111I 1111111111111111111111111111111111 III
3234
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33
1 3
330 p,s
• -- • v- • -~
7 272 7 27
DOT (P5/39)
2 3
4
5
6
7
8
9
10
11 12
14 15
PIN (P5/27)
~11/
210 p,s
250 p,s
t
250 p,S
t
250 p,S
The diagram above shows what happens when character lA' is printed. Dot pulses 1 -7,10-16,
19 - 25 and 28 - 34 are synchronized to activate the PIN signal.
8