Rev. 1.00
48
August 29, 2018
Rev. 1.00
49
August 29, 2018
HT45F6530
AC Voltage Regulator Flash MCU
HT45F6530
AC Voltage Regulator Flash MCU
“
CLR WDT
”
Instruction
WE4~WE0 bits
WDTC Register
Reset MCU
f
LIRC
CLR
“
HALT
”
Instruction
LIRC
8-stage Divider
WDT Prescaler
f
LIRC
/2
8
8-to-1 MUX
WS2~WS0
WDT Time-out
(2
8
/f
LIRC
~2
15
/f
LIRC
)
Watchdog Timer
Reset and Initialisation
A reset function is a fundamental part of any microcontroller ensuring that the device can be set
to some predetermined condition irrespective of outside parameters. The most important reset
condition is after power is first applied to the microcontroller. In this case, internal circuitry will
ensure that the microcontroller, after a short delay, will be in a well-defined state and ready to
execute the first program instruction. After this power-on reset, certain important internal registers
will be set to defined states before the program commences. One of these registers is the Program
Counter, which will be reset to zero forcing the microcontroller to begin program execution from the
lowest Program Memory address.
In addition to the power-on reset, another reset exists in the form of a Low Voltage Reset, LVR,
where a full reset is implemented in situations where the power supply voltage falls below a
certain threshold. Another type of reset is when the Watchdog Timer overflows and resets the
microcontroller. All types of reset operations result in different register conditions being setup.
Reset Functions
There are several ways in which a microcontroller reset can occur, through events occurring
internally:
Power-on Reset
The most fundamental and unavoidable reset is the one that occurs after power is first applied to
the microcontroller. As well as ensuring that the Program Memory begins execution from the first
memory address, a power-on reset also ensures that certain other registers are preset to known
conditions. All the I/O port and port control registers will power up in a high condition ensuring that
all pins will be first set to inputs.
V
DD
Power-on Reset
SST Time-out
t
RSTD
Note: t
RSTD
is power-on delay, typical time=50ms.
Power-on Reset Timing Chart
