Toshiba DP120F, Service Manual

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March 2000 © TOSHIBA TEC 7-35 DP120F/DP125F Circuit Description
3.5 Reset Circuit
When the logic voltage is unstable as the power switch is turned on, and so on, or an abnormal
condition has occurred in the system, the reset circuit resets the respective IC’s to prevent them
from malfunctioning.
When the voltage of +5V supplied from the LVPS is +4.2V or under, the output of the RESET IC
(IC24) will go LOW and the PWRESETX signal will go LOW. This causes Q246 to turn on to
reset the CPU (IC66). The RES1 signal and RESETX signal will also go LOW to reset the
DMAC GA (IC16), PTC GA (IC45), and so on.
In case an abnormal condition has occurred in the system and the CPU crashes, the DMAC GA
causes the ROUTX signal to go LOW. This causes the system to be reset in the same manner
as when the power is turned on.
07-03-05
Fig. 7-3-5
Signal Name Type Active Description Destination
PWRESETX O L Power on Reset Signal IC2
RESETX O L Reset Signal Each IC
ROUTX O L Watchdog Reset Signal IC2