Samsung SF-4500 Service Manual page 41

6-1-2-10. RESET CIRCUIT
As for this product, there are 2 power resets of pri-
mary 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
(KS32C6200) after primary
supply
Voltage
/F-POR
/POR
PnRST
(internal)
Reset
ROM Access
• POWER MONITOR (U103: KIA7045F)
If +5V supplied to KIA7045F is so unstable as to
reach +4.65V - +4.35V (typically 4.5V), it will
recognize it as power failure. Then KIA7045F
output terminal becomes low (0V) and the voltage
is impressed to flash memory and KS32C6200, run-
ning RESET (LOW ACTIVE). Flash memory and
6-10
Reset filter
65 MCLK
Fig.6-1-10 POWER RESET TIMING DIAGRAM
reset. Primary reset makes flash memory wait in
READ mode to fetch program
codes, and secondary reset makes the main
controller (KS32C6200) wake up and initialize
external peripherals to operate the system.
Fig.5-1-10 is Power Reset Timing Diagram.
Internal Reset
256 MCLK
KS32C6200 are reset first. Thereafter modem, print
control parts and SCANIP(Color Image Processor)
linked to /RSTOUT terminal of KS32C6200 are
reset as well. KIA7045F output
terminal of open drain structure is pulled up 5.1kΩ
and put out.
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