HT49RA1_14 Datasheet, PDF (40/57 Pages) Holtek Semiconductor Inc – Remote Type 8-Bit MCU with LCD

HT49RA1/HT49CA1
There are two methods of using software instructions to
clear the Watchdog Timer, one of which must be chosen
by configuration option. The first option is to use the sin-
gle ²CLR WDT² instruction while the second is to use the
two commands ²CLR WDT1² and ²CLR WDT2². For the
first option, a simple execution of ²CLR WDT² will clear
the WDT while for the second option, both ²CLR WDT1²
and ²CLR WDT2² must both be executed to successfully
clear the WDT. Note that for this second option, if ²CLR
WDT1² is used to clear the WDT, successive executions
of this instruction will have no effect, only the execution of
a ²CLR WDT2² instruction will clear the WDT. Similarly
after the ²CLR WDT2² instruction has been executed,
only a successive ²CLR WDT1² instruction can clear the
Watchdog Timer.
Configuration Options
Configuration options refer to certain options within the MCU that are programmed into the device during the program-
ming process. During the development process, these options are selected using the HT-IDE software development
tools. As these options are programmed into the device using the hardware programming tools, once they are selected
they cannot be changed later as the application software has no control over the configuration options. All options must
be defined for proper system function, the details of which are shown in the table.
Item
Options
I/O Options
1
PB0~PB7: wake-up enable or disable (bit option)
2
PC0: CMOS output or carrier output (bit option)
3
PC0: Pull-high enable or disable (bit option)
LCD Options
4
LCD clock: f_S/2², f_S/2³, f_S/2⁴, f_S/2⁵, f_S/2⁶, f_S/2⁷, f_S/2⁸
5
LCD duty: 1/2, 1/3, 1/4
6
LCD bias: 1/2, 1/3
7
LCD segment 12~15 output or CMOS output(Nibble Option)
8
LCD segment 16~19 output or CMOS output(Nibble Option)
Interrupt Options
9
INT0 function: enable or disable
10
Triggering edge: rising, falling or both
11
INT1 function: enable or disable
12
Triggering edge: rising, falling or both
Oscillator Options
13
f_S internal clock source: RTC oscillator, WDT oscillator or f_SYS/4
Timer Options
14
Timer/Event Counter 0 clock source: f_SYS or f_SYS/4
Time Base Options
15
Time Base division ratio: f_S/2¹², f_S/2¹³, f_S/2¹⁴, f_S/2¹⁵
Watchdog Options
16
WDT enable or disable
17
CLRWDT instructions: 1 or 2 instructions
Rev. 1.10
40
March 30, 2014