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PRINT EMITTER CONTROL AND PRINT TIMINGS
The MPU uses the print emitter control circuits to
measure time between emitter pulses (for checking
purposes), to measure the time for firing the print wires
(approximately 384 ms), and to sense the direction of
emitter pickup movement.
Print emitter control circuits include a counter used in
checking for emitter pulses too close together
(fast-speed check). An elapsed-time counter is used in
checking for pulses too far apart (slow-speed check or
no-emitter-pulses check).
At each emitter pulse, a counter is incremented
(decremented for right-to-Ieft motion) causing, the
address to the character generator to point to the group
of print wires to be fired. The low order 8 bits of the
counter address the character. The high-order 4 bits
are used as a counter to step through the character.
When a character boundary is detected, the M PU
changes the counter to address and step through the
next character.
Timing relationships of the driver signals vary from
those of the left margin, print emitter, and print wires.
The timing relationship among left margin, print emitter,
and print wire signals do not vary.
The following example shows the' -print emitter 2' as
the first active pulse; it could be any of the 3 pulses,
depending on where the print emitter pickup is aligned
with the print emitter. Print emitter pulses are sent to
the adpater to indicate 0.25 mm (0.010 inch) of print
head travel along the print line.
4-18
Objective: To start print head motion from the left
margin, print an A in character position 1 and print a 8
in character position 2.
. .
Carrier stepper motor drive lines' -not A carrier dr'
and' -not 8 carrier dr' are active for 50 ms settling
time; '-A carrier dr' and' -8 carrier dr' are
inactive.
II
Print head left-to-right start sequence begins
(' -not A carrier dr' becomes inactive, '-A carrier
dr' becomes active).
II
Print emitter pulses are generated when the carrier
motor moves the print emitter pickup. Moving left
to right generates a count-up sequence (1, 2, 3).
. .
The' -left margin' line goes inactive between the
'-print emitter 3' pulses.
II
Printing starts (in character position 1) on the next
'-print emitter 3' pulse after the' -left margin' line
goes inactive. The adapter uses the print emitter
pulses to synchronize the firing of the print wire
solenoids.
II
The adapter pulses the print wire lines for
approximately 384 ms (between 375 and 400 '
microseconds) in synchronization with the print
emitter pulses to form a character within an
8-high by 7-wide matrix.
II
Three print emitter pulses separate a character
position.
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