Brother PT-2500PC, Service Manual

Page: 64 / 79

III - 14
3.2.13 Reset Circuit
Fig. 3.2-14 shows the reset circuit. This circuit prevents the CPU and logic circuitry from
malfunctioning in powering-on and -off sequences.
Fig. 3.2-15 shows the reset timing when the power is first applied or cut off.
Plugging the AC line adapter in the DC jack raises the Vcc which feeds power to the
CPU and the logic circuitry. When the Vcc reaches approx. 4.2V (point "A" in Fig. 3.2-
15), the reset IC (S-80842ANUP, Q2) operates to turn the RESET from Low to High.
When the power is cut off so that the Vcc drops below approx. 4.2V (point "B"), the
RESET turns from High to Low.
Fig. 3.2-14 Reset Circuit
Fig. 3.2-15 Reset Timing