
CHAPTER 25 RESET FUNCTIONS
User’s Manual U16541EJ4V0UD
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25.3.3 Reset operation by low-voltage detector
If the supply voltage falls below the voltage detected by the low-voltage detector when LVI operation is enabled, a
system reset is executed (when the LVIM.LVIMD bit is set to 1), and the hardware is initialized to the initial status.
The reset status lasts from when a supply voltage drop has been detected until the supply voltage rises above the
LVI detection voltage.
The main clock oscillator is stopped during the reset period.
When the LVIMD bit = 0, an interrupt request signal (INTLVI) is generated if a low voltage is detected.
Table 25-3. Hardware Status During Reset Operation by Low-Voltage Detector
Item
During Reset
After Reset
Main clock oscillator (fX)
Oscillation stops
Oscillation starts
Subclock oscillator (fXT)
Oscillation continues
Internal oscillator
Oscillation stops
Oscillation starts
Peripheral clock (fX to fX/1,024)
Operation stops
Operation starts after securing oscillation
stabilization time
Internal system clock (fXX),
CPU clock (fCPU)
Operation stops
Operation starts after securing oscillation
stabilization time (initialized to fXX/8)
CPU
Initialized
Program execution starts after securing
oscillation stabilization time
Watchdog timer 2
Operation stops (initialized to 0)
Counts up from 0 with internal oscillation
clock as source clock.
Internal RAM
Undefined if power-on reset or CPU access and reset input conflict (data is damaged).
Otherwise value immediately after reset input is retained
Note.
I/O lines (ports/alternate-function
pins)
High impedance
On-chip peripheral I/O register
Initialized to specified status, OCDM register retains its value.
LVI
Operation stops
On-chip peripheral functions other
than above
Operation stops
Operation can be started after securing
oscillation stabilization time.
Note
The firmware of the V850ES/SG2 uses part of the internal RAM after the internal system reset operation
has been released because it supports a boot swap function. Therefore, the contents of some RAM areas
are not retained on power-on reset. For details, see 25.3.4 Operation after reset release.
Remark
The reset timing of the low-voltage detector, see CHAPTER 27 LOW-VOLTAGE DETECTOR (LVI).