HT48R068B Datasheet, PDF (40/121 Pages) Holtek Semiconductor Inc – Enhanced I/O Type 8-bit OTP MCU

HT48R068B/HT48R069B
Enhanced I/O Type 8-bit OTP MCU
C L R W D T 1 F la g
C L R W D T 2 F la g
1 o r 2 In s tr u c tio n s
fS Y S /4
LX T
L IR C
W D T C lo c k S o u r c e S e le c tio n
C le a r W D T T y p e
C o n fig u r a tio n O p tio n
C o n fig .
O p tio n
S e le c t
fW D T C K
C LR
1 5 s ta g e c o u n te r
W S 2~W S 0
Watchdog Timer
W D T T im e - o u t
●● WDTS Register
Bit
7
6
5
4
Name
—
—
—
—
R/W
—
—
—
—
POR
—
—
—
—
Bit 7~3
unimplemented, read as "0"
3
2
—
WS2
—
R/W
—
1
Bit 2~0
WS2, WS1, WS0: WDT time-out period selection
000: 2⁸ t_WDTCK
001: 2⁹ t_WDTCK
010: 2¹⁰ t_WDTCK
011: 2¹¹ t_WDTCK
100: 2¹² t_WDTCK
101: 2¹³ t_WDTCK
110: 2¹⁴ t_WDTCK
111: 2¹⁵ t_WDTCK
1
WS1
R/W
1
0
WS0
R/W
1
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, situations may arise where it is necessary to forcefully apply
a reset condition when the microcontroller is running. One example of this is where after power
has been applied and the microcontroller is already running, the RES line is forcefully pulled low.
In such a case, known as a normal operation reset, some of the microcontroller registers remain
unchanged allowing the microcontroller to proceed with normal operation after the reset line is
allowed to return high. 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.
Another reset exists in the form of a Low Voltage Reset, LVR, where a full reset, similar to the
RES reset is implemented in situations where the power supply voltage falls below a certain
threshold.
Rev 1.00
35
February 14, 2011