HT45F12_12 Datasheet, PDF (46/103 Pages) Holtek Semiconductor Inc – 8-Bit Flash MCU with Op Amps & Comparators

HT45F12
8-Bit Flash MCU with Op Amps & Comparators
Bit 2 ~ 0
WS2 ~ WS0: Select WDT Timeout Period
000: 2⁸/fS
001: 2¹⁰/fS
010: 2¹²/fS
011: 2¹⁴/fS
100: 2¹⁵/fS
101: 2¹⁶/fS
110: 2¹⁷/fS
111: 2¹⁸/fS
These three bits determine the division ratio of the Watchdog Timer source clock,
which in turn determines the timeout period.
CTRL Register
Bit
7
6
5
4
3
2
1
0
Name FSYSON —
—
—
—
LVRF
LRF
WRF
R/W
R/W
—
—
—
—
R/W
R/W
R/W
POR
0
—
—
—
—
x
0
0
Bit 7
Bit 6~3
Bit 2
Bit 1
Bit 0
FSYSON: fSYS Control in IDLE Mode
Describe elsewhere.
Unimplemented, read as “0”
LVRF: LVR function reset flag
Describe elsewhere.
LRF: LVR Control register software reset flag
Describe elsewhere.
WRF: WDT Control register software reset flag
0: Not occur
1: Occurred
This bit is set to 1 by the WDT Control register software reset and cleared by the
application program. Note that this bit can only be cleared to 0 by the application
program.
Watchdog Timer Operation
The Watchdog Timer operates by providing a device reset when its timer overflows. This means
that in the application program and during normal operation the user has to strategically clear the
Watchdog Timer before it overflows to prevent the Watchdog Timer from executing a reset. This is
done using the clear watchdog instructions. If the program malfunctions for whatever reason, jumps
to an unknown location, or enters an endless loop, these clear instructions will not be executed in the
correct manner, in which case the Watchdog Timer will overflow and reset the device. A Watchdog
Timer configuration option determines if the Watchdog Timer is always enabled or if it is enabled
using the application program. With regard to the Watchdog Timer enable/disable function, there are
also five bits, WE4~WE0, in the WDTC register to offer additional enable/disable and reset control
of the Watchdog Timer. If the WDT configuration option has selected that the WDT function is
always enabled, then WE4~WE0 bits still have effect on the WDT function. When the WE4~WE0
bits value are equal to 01010B or 10101B, the WDT function is enabled. However, if the WE4~WE0
bits are changed to any other values except 01010B and 10101B, which could be caused by adverse
environmental conditions such as noise, it will reset the microcontroller after 2~3 LIRC clock
cycles. If the WDT configuration option has selected that the WDT function is controlled using the
Rev. 1.20
46
February 27, 2013