
CHAPTER 25 RESET FUNCTIONS
Preliminary User’s Manual U16541EJ1V0UM
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25.3 Operation
25.3.1 Reset operation via RESET pin
When a low level is input to the RESET pin, the system is reset, and each hardware unit is initialized.
When the level of the RESET pin is changed from low to high, the reset status is released.
If the reset status is released by RESET pin input, the oscillation stabilization time elapses (reset value of OSTS
register: 2
16/fX) and then the CPU starts program execution.
Table 25-1. Hardware Status on RESET Pin Input
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 of oscillation
stabilization time
Internal system clock (fXX),
CPU clock (fCPU)
Operation stops
Operation starts after securing of oscillation
stabilization time (initialized to fXX/8)
CPU
Initialized
Program execution starts after securing of
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 registers
Initialized to specified status, OCDM register is set (01H).
Other on-chip peripheral functions
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.
Caution
The V850ES/SG2 may enter on-chip debug mode (flash memory version only) after the reset
status has been released, depending on the pin status. For details, see CHAPTER 4
PORT
FUNCTIONS.