IBM 5256-1 Maintenance Information Manual page 147

Carrier (Print Head) Movement
The carrier motor, which provides the carrier (print head)
movement, is driven by 4 lines from the printer adapter:
'A carrier dr', , not A carrier dr', , 8 carrier dr', and ' not 8
carrier dr'.
When the print head is starting, printing, stopping, or
settling, only
2
of the
4
drive lines are active at one
time. When the carrier is stopped for a time greater
than the settling time, none of the 4 lines are active.
Each time the status (phase) of the 4 lines is changed,
the motor rotates
2
degrees. The time that the lines
stay in each phase is controlled by the microprocessor.
After carrier (print head) movement, 2 drive lines stay on
during settling time (50 milliseconds). This ensures that
movement has stopped and the correct movement
occurs when the next printer operation starts.· A settle
time is also needed at the start of carrier movement.
If there is no printer operation waiting, the carrier drive
lines are de-activated after the settling time of the
current printer operation. If there is no printer operation
for more than 2 minutes and the Ready light is on, the
print head is returned to the ramped position. The
Ready light remains on. This timeout does not apply
when the printer is in a stop or not ready condition.
Start, Move Left to Right, and Stop
When power is first applied, the carrier drivers 'not A'
and ' not 8' ·are activated by the adapter for 50
milliseconds. This locks the motor for a settling time to
ensure that the print head is stopped and will move
correctly when the carrier stepper motor is advanced.
Other than a power on sequence, the start sequence
can begin on any of the 4 active carrier driver conditions
('A' and '8', 'not A' and '8', 'not A' and 'not 8', 'A' and
'not 8'), but the active start condition must be the same
as the previous settling time.
4-26
To advance the stepper motor clockwise and move the
print head left to right, the carrier predrivers are turned
on and off in sequence as shown .. Up-to-speed motor
advance pulses are
3.27
ms apart at
40
and
80
cps. At
this motor speed, print emitter pulses are spaced about
2.50 ms apart when printing at 40 cps and about 1.25
ms apart when printing at
80
cps. Up-to-speed motor
advances for 120 cps operation are 2.15 ms apart and
print emitter pulses are spaced 0.83 ms apart.
To stop the print head movement, the carrier stepper
motor must go through a stop sequence that includes
slowing the motor and locking it for a settling time.
Move Right to Left
To turn the carrier stepper motor counterclockwise and
move the print head right to left, the carrier predrivers
are turned on and off in sequence (see the following
illustration). The start and stop timings are the same as
when moving the print head left to right.
Start and Stop Sequences
The motor is started slowly and slowed before stopping.
At the beginning (start sequence) and ending (stop
sequence) of print head motion, the carrier stepper
motor must be locked for a settling time. This ensures
that the print head is not moving and will move correctly
when it is restarted. The settling time depends on the
frequency of print activity. Settling time is normally 50
ms but it might be as long as 150 ms.
Right Margin Stop
When moving the print head left to right, the adapter
must start a stop sequence (see the following figure)
immediately after character position
132
to ensure that
the print head does not touch the mechanical stop in
the right margin.