HT66F24D View Datasheet(PDF) - Holtek Semiconductor
Part Name
Description
MFG CO.
'HT66F24D' PDF : 177 Pages View PDF
A/D Flash Type 8-bit MCU with EEPROM
HT66F24D/HT66F25D
Bit 2~0
WS2~WS0: WDT Time-out period selection
000: 28/fS
001: 210/fS
010: 212/fS
011: 214/fS
100: 215/fS
101: 216/fS
110: 217/fS
111: 218/fS
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. Some
of the Watchdog Timer options, such as always on select and clear instruction type are selected
using configuration options. 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 is determined that the WDT
function is always enabled, the WE4~WE0 bits still have effects on the WDT function. When the
WE4~WE0 bits value is 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 is caused by
the environmental noise, it will reset the microcontroller after 2~3 LIRC clock cycles. If the WDT
configuration option is determined that the WDT function is controlled by the WDT control register,
the WE4~WE0 values can determine which mode the WDT operates in. The WDT function will be
disabled when the WE4~WE0 bits are set to a value of 10101B. The WDT function will be enabled
if the WE4~WE0 bits value is equal to 01010B. If the WE4~WE0 bits are set to any other values by
the environmental noise, except 01010B and 10101B, it will reset the device after 2~3 LIRC clock
cycles. After power on these bits will have the value of 01010B.
Rev. 1.10
51
March 25, 2013
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