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11.
Operation and Description for each part of the Circuit
11-3 RESET and Power
Fail circuit
11-3-1
Reset Circuit
Reset signal is a signal in order to start-up CPU
under Power-on, and Reset circuit uses an Reset
IC M51953(U10). When +5V is fallen under 4.3V
by Power-off, RESET signal prohibits the system
from misoperating by lowering down to OV.
Figure 11-4 RESET\
waveform
11-3-2
Power Fail Sensing Circuit
Power Fail Sensing Circuit senses sudden power-
off to backup the needed data and current CPU
status into RAM before 40ms after +5V drops.
When power is turned on, the CPU does the
operations which were working before power-off.
This system is esigned to sense the time when the
printer driving voltage +25V goes down to +15V.
Power-On
Power-Oft
+25V
:
P-Fail © a
eee)
ce
—> <—
40ms
Figure 11-5. Power Fail Waveform
11-4 Battery, RTC(Clock), Buzzer, Turret Driving Circuit
11-4-1
Battery Circuit
BATTERY Circuit supplies SRAM and RTC (U27,
RP5C15) with voltage source and is used to drive
Clock and to save DATA when the main Power is
turned off. When the Power is turned on, VCC
source(+5V) is supplied to SRAM, RTC, through
the D4 and the Battery is charged, when the Power
is turned off, D4 is shut and the source charged in
the Battery is supplied to SRAM and RTC,
11-4-2 RTC(Clock) Circuit
This uses an Clock IC RP5C15, is driven by the
Battery when the main Power is turned off, and
the frequency 32.768kHz made by X2, C30, C31
inputs to this circuit.
11-2
Samsung
SER-6500/ SER-6500F / SER-6540 / SER-6540F
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