Brother PT-9200PC, Руководство по обслуживанию, Страница: 68 / 93

III - 5
3.2.3 Logic and VH Power, and Related Circuits
Power from a commercially available wall outlet is Vcc (+5V±0.25V) which is
supplied to the main PCB, and then to all logic components.
When Vcc is supplied, the reset IC (Q7) switches the reset signal level to high to
start the CPU.
When the CPU starts after the power is supplied, ports are initialized, and the CPU
enters the sleep state (the power is turned off).
With the power off, pressing the ON/OFF key causes the interruption of NMI to start
the CPU, turning on the power.
With the power on, pressing the ON/OFF key places the CPU in the sleep state (the
power is turned off).
With the machine in operation, P83 is switched to high to turn on Q9 (FET),
supplying VH to the thermal head, the full cutter motor, the half cutter motor, and
the tape feed motor.
3.2.4 Stepping Motor (Tape Feed Motor) Drive Circuit
Fig. 3.2-3 shows the stepping motor drive circuit.
The Ø25 stepping motor is used to feed the ribbon and the tape. The stepping
motor feeds the tape 1/720 in. for one pulse (one dot for two pulses).
Drive pulses are transmitted from P104-P107 of the CPU (#5) to Q1-Q4 to drive the
motor with a unipolar 2-2 phase excitation (AB
→
DA
→
CD
→
BC forward feed).
(1) Printing at fixed speed
The rate of fixed speed printing, at which printing is performed while the tape is
fed at a fixed speed, is 571 pps (1.75 msec/pulse).
The through-up pulses (including pre-excitation) and through-down pulses
(including post-excitation) are 56 and 5 pulses, respectively.
(2) Halfway stop of printing
If printing is stopped halfway, the circuit continuously drives the motor (overrun
for 198 pulses) after the stop, then shuts off the power.