Xerox WorkCentre XK50cx Service Manual page 36

RESET CIRCUIT
As for XK50CX, there are two power resets of
primary reset(/F-POR) and secondary reset(/POR)
and also reset by watchdog timer (/RSTO). Primary
reset is used to initialize flash memory when the
system is turned on, while secondary reset is used
to initialize the whole system by initializing MFP
controller (KS32C6400) after primary reset.
• POWER MONITOR (U13)
If +5V supplied to U13 is so unstable as to reach
+4.65V - +4.35V (typically 4.5V), it will
recognize it as power failure. Then XC61A-5
output terminal becomes low (0V) and the voltage
is impressed to flash memory and KS32C6400,
running RESET (LOW ACTIVE). Flash memory
Fig.4-1-8 POWER RESET TIMING DIAGRAM
Primary reset makes flash memory wait in READ
mode to fetch program
codes, and secondary reset makes the main
controller (KS32C6400) wake up and initialize
external peripherals to operate the system.
Fig.4-1-8 is Power Reset Timing Diagram.
and KS32C6400 are reset first. Thereafter, print
control parts and DUOIP (Color Image Processor)
linked to /RSTOUT terminal of KS32C6400 are
reset as well. U13 output terminal of open drain
structure is pulled up 1MΩ and put out.
Circuit
4-9