SN32F760 Series
32-Bit Cortex-M0 Micro-Controller
SONiX TECHNOLOGY CO., LTD
Page 40
Version 2.0
3
3
3
SYSTEM CONTROL
3.1 RESET
A system reset is generated when one of the following events occurs:
1.
A low level on the RST pin (external reset).
2.
Power-on reset (POR reset)
3.
LVD reset
4.
Watchdog Timer reset (WDT reset)
5.
Software reset (SW reset)
6.
DPDWAKEUP reset when exiting Deep power-down mode by DPDWAKEUP pin
The reset source can be identified by checking the reset flags in
System Reset Status register (SYS0_RSTST)
These sources act on the RST pin and it is always kept low during the delay phase. The RESET service routine vector
is fixed at address 0x00000004 in the memory map. For more details, refer to
Interrupt and Exception Vectors
Finishing any reset sequence needs some time. The system provides complete procedures to make the power on reset
successful. For different oscillator types, the reset time is different. That causes the VDD rise rate and start-up time of
different oscillat
or is not fixed. RC type oscillator’s start-up time is very short, but the crystal type is longer. Under client
terminal application, users have to take care of the power on reset time for the master terminal requirement. The reset
timing diagram is as following.
VDD
VSS
VDD
VSS
Watchdog Normal Run
Watchdog Stop
System Normal Run
System Stop
LVD Detect Level
External Reset
Low Detect
External Reset
High Detect
Watchdog
Overflow
Watchdog
Reset Delay
Time
External
Reset Delay
Time
Power On
Delay Time
Power
External Reset
Watchdog Reset
System Status
3.1.1
POWER-ON RESET (POR)
The power on reset depends on LVD operation for most power-up situations. The power supplying to system is a rising
curve and needs some time to achieve the normal voltage. Power on reset sequence is as following:
Power-up:
System detects the power voltage up and waits for power stable.
External reset (only external reset pin enable):
System checks external reset pin status. If external reset pin is
not high level, the system keeps reset status and waits external reset pin released.
System initialization:
All system registers is set as initial conditions and system is ready.
Oscillator warm up:
Oscillator operation is successfully and supply to system clock.
Program executing:
Power on sequence is finished and program executes from Boot loader.
