Mitsubishi DS907x SIP User Manual page 62

USER'S GUIDE
The original contents of those Special Function regis-
ters that are initialized by a reset are lost.
Voltage Monitoring Circuitry
The on–chip voltage monitoring circuitry automatically
places the microprocessor in its Data Retention state in
the absence of V . It insures that the proper internal
CC
control signals are generated and that power from the
lithium cell is applied at the proper times so that the Pro-
gram/Data RAM, data in the Scratchpad Registers and
certain Special Function Registers remain unchanged
when V is cycled on and off. In addition, an interrupt is
CC
available for signaling the processor of an impending
SECURE MICROCONTROLLER POWER CYCLING TIMING Figure 7–2
V
CC
V
PFW
V
CCMIN
V
INTERRUPT
SERVICE
ROUTINE
CLOCK
OSC.
INTERNAL
RESET
LITHIUM
CURRENT
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t
F
power fail condition so that the operational state of the
processor can be saved just prior to entering the Data
Retention.
The voltage monitoring circuitry recognizes three volt-
age thresholds below nominal operating voltage. These
thresholds are identified as V
voltage), V (minimum operating voltage), and V
CCmin
(lithium supply) voltage. These thresholds are used to
initiate required actions within the microprocessor dur-
ing situations when V
timing diagram shown in Figure 7–2 illustrates key inter-
nal activities during power cycling.
t
CSU
62
(Power Fail Warning
PFW
power is cycled on and off. The
CC
t
POR
LI