Table of Contents
Advertisement
Forms Movement
Forms movement is controlled by the microprocessor.
Forms are moved by a forms motor that is geared to the
platen. When the forms are moved, the forms emitter
sends pulses to the printer adapter to advance the
stepper motor.
When the MPU recognizes a line feed request, it
samples the forms emitters. If the printer is in ready
state, the emitters are compared to the value of the last
detent. If the value is unchanged or only one motor
phase different, a pre-detent of up to 250 ms is started
to realign the forms. When the emitters are correct, the
line feed is started.
If the printer is not in ready state, the emitters are
stored as the value to be used for comparison and no
pre-detent is needed.
The line feed is started by setting the index bit in the
forms register. The output of the register bit latch gates
the forms emitter lines to the forms motor drivers.
The proper stepping sequence is as follows:
Step 1 - 'A' and 'not B'
Step 2 - 'A' and 'B'
Step 3 - 'not A' and 'B'
Step 4 - 'not A' and 'not B'
For each 1.05 mm (1/24 inch) of forms travel, the
motor drive lines will match the value previously stored ..
These matches are counted and the count is used for
stopping the motor for 6 or 8 lines per inch spacing.
Stopping after a count of 4 produces the 6-line spacing.
Stopping after a count of 3 produces the 8-line spacing.
The MPU sets up the forms control logic so that if the
motor has been moved 2 or more motor phases (by
paper tension or the operator) a forms check is signaled
and the MPU displays a forms position check. If the
motor has been moved 1 motor phase, the M PU will
detent the motor before line feeding starts. If the motor
has not moved, line feeding will start immediately.
The normal way to obtain a line feed from the Line Feed
switch is to first press the Stop switch and then press
the Line Feed switch. If the Stop switch is pressed
while a print operation is in progress, the line of printing
is completed and the printer stops. The Line Feed
switch must then be pressed again to obtain a line feed.
To stop forms movement, the motor stepping sequence
is reversed for 1 ms under microprocessor control.
Following this, 50 ms of settling time is allowed before
starting a print operation. The following timing chart
shows the tiFT1ing for 1 forward space at 6 lines per 25.4
mm (1 inch) and the ending settle time.
Theory,
Features
Theory
5256 MIM
4-39
Advertisement
Table of Contents
