Tape Feed Motor Drive Circuit - Brother PT-2500PC Service Manual

3.2.4

Tape Feed Motor Drive Circuit

Fig. 3.2-3 shows a drive circuit of the tape feed motor which feeds tape and ink ribbon.
The motor is a 30-mm in diameter, 24-pole, and 108-internal resistance stepping motor.
This circuit drives the motor with a bipolar 2-2 phase excitation.
The CPU (#3) controls the motor rotation direction with signals on P104 and P105 and
turns the motor on and off with an activation signal of the driver IC (TA7774F, #2). When
P106 is High, the motor rotates in the direction defined by the signals on P104 and
P105.
(1) Printing in a constant speed
For regular printing in a constant speed, the CPU drives the motor at the rate of 144
pps.
acceleration and deceleration are programmed to consume 8 and 3 pulses,
respectively.
(2) Printing interrupt (margin cutting drive and buffer full drive)
After completion of the current printing, the CPU brakes the motor with 3-pulse
gradual deceleration and then counter-drives it by 20 pulses to stop the motor.
To provide buffered starting and stopping for the motor, the gradual
Fig. 3.2-3 Tape Feed Motor Drive Circuit
III - 6