
CHAPTER 25 RESET FUNCTIONS
Preliminary User’s Manual U16541EJ1V0UM
800
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 LVIMD bit of the LVIM register 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 detector.
Following reset release, the CPU starts program execution after securing the
oscillation stabilization time (initial value of OSTS register: 2
16/fX) of the main clock oscillator.
The main clock oscillator is stopped during the reset period.
Table 25-3. Hardware Statuses 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
Ring-OSC generator
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
Operation starts
Internal RAM
Undefined if power-on reset or writing data to RAM (by CPU) 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 swapping function. Therefore, the contents of some RAM
areas are not retained on power-on reset.