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Rev.1.02
Nov 26, 2008
REJ03B0224-0102
455A Group
VOLTAGE DROP DETECTION CIRCUIT (WITH SKIP
JUDGMENT)
The built-in voltage drop detection circuit is used to set the
voltage drop detection circuit flag (VDF) or to perform system
reset.
Fig 53. Voltage drop detection reset circuit
(1) Operating state of voltage drop detection circuit
The voltage drop detection circuit becomes valid by inputting
“H” to the VDCE pin and it becomes invalid by inputting “L.”
When not executing the SVDE instruction under “H” level of the
VDCE pin, the voltage drop detection circuit become invalid in
power down state (RAM back-up, clock operating mode). As for
this, the voltage drop detection circuit becomes valid at returning
from power down, again.
When executing the SVDE instruction under “H” level of the
VDCE pin, the voltage drop detection circuit becomes valid in
power down state (RAM back-up, clock operating mode).
The state of executing SVDE instruction can be cleared by
system reset.
Note. “O” indicates valid, “×” indicates invalid.
Notes 1:
This symbol represents a parasitic diode.
2:
Applied potential to VDCE pin must be VDD or less.
(Note 1)
VDCE
(Note 2)
Internal reset signal
T3UDF
Key-on wakeup signal
S
R
Q
S
R
Q
SVDE instruction
Internal reset signal
Q
VSKIP
+
Voltage drop
detection circuit
VRST-/VRST+
+
Reset occurrence
Flag occurrence
VDF
Skip judgement
VDD
Voltage drop detection
circuit reset signal
Voltage drop detection
circuit flag
EPOF instruction + POF instruction
EPOF instruction + POF2 instruction
Oscillation stop signal
Table 22 Operating state of voltage drop detection circuit
VDCE pin
SVDE instruction
at CPU operating
at power down
“L”
No execute
×
Execute
×
“H”
No execute
O
×
Execute
O