7-7
Reset Circuit
The reset circuit is used to prevent the CPU from operating erratically and the print head from printing unexpectedly
during the period of unstable voltage immediately after the pwer is turned on. To accomplish this, the OUT terminal
output (pin 6) of the reset IC (U4) is supplied to the CPU (U12) as the RESET input signal (pin 28), and is supplied to
the gate array (U19) as the RESET input signal (pin 1). The output (pin 6) is also supplied as the switching signal for
controlling the +24V power supply circuitry.
The reset IC (U4) monitors the +5V voltage; when the voltage is 4.5V or more, the reset is released for the CPU and
other components and the printer becomes ready.
Reset IC output becomes low and CPU is reset if I/F reset signal (nlnit, #31) is supplied more than 50 µs when the host
is at forward transmission (when I/F signal 1284ACT, #36 is low).
Figure 7-5. TM-U375P Reset Circuit Diagram
CPU
Table 7-4. TM-U375P CPU Pin Functions
CONFIDENTIAL
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