HT46R71D-1 Holtek Semiconductor, HT46R71D-1 Datasheet - Page 12

• Manufacturer Part Number: HT46R71D-1
• Description: Dual Slope A/D Type MCU
• Manufacturer: Holtek Semiconductor

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external resistor between OSC1 and VSS is required to
achieve oscillation, the value of which must be between
100k to 2.4M . The system clock divided by 4, which
can be monitored on pin OSC2, can be used for external
logic synchronization purposes.
The Internal RC oscillator (Int.RCOSC) is a free running
on-chip RC oscillator, requiring no external compo-
nents. Even if the system enters the Power Down Mode,
and the system clock is stopped, the internal RC oscilla-
tor continues to run with a period of approximately 65 s
at 5V if either the WDT or IRC clock is enabled. The in-
ternal RC oscillator can be disabled by a configuration
option and by clearing the IRCC bit to 0 to conserve
power.
Watchdog Timer - WDT
The WDT is implemented using a dedicated internal RC
oscillator (Int. RCOSC, note: the WDTOSC described in
this document represents the same oscillator as the
Int.RCOSC) or the instruction clock which is the system
clock/4. The timer is designed to prevent a software
malfunction or sequence from jumping to an unknown
location with unpredictable results. The watchdog timer
can be disabled by a configuration option. If the watch-
Note: WDTOSC registers initial value will be set to enable (1,0), if both WDT option enable and WDT clock option
The WDT clock (f
sion ratio can be varied by selecting different configuration options to give 2
Rev. 1.00
Bit No.
Bit No.
0~1
2~3
4~7
0~7
set to WDT , otherwise, it will be set to disable (0,1)
WDTPWR0~
WDTPWR0~
WDTPWR1
WDTPWR7
WDTOSC0~
WDTOSC1
Label
Label
S1
) is further divided by an internal counter to give longer watchdog time-outs., In this device, the divi-
The WDT Power source selection. (WDTPWR1:0)=
01: WDT power comes from VOCHP
10: WDT power comes from regulator
00/11: WDT power comes from VOCHP strongly recommend use to use 01 for VOCHP
prevent the noise to let the WDT lose the power
The WDT oscillator enable/disable (WDTOSC1:0)=
01: WDT OSC disable10: WDT OSC enable
00/11: WDT OSC enable strongly recommend use to use 10 for WDT OSC enable
Reserved
The WDT counter data value.
This register is read only. It s used for temperature adjusting.
WDTC (1CH) Register
WDTD (1DH) Register
12
dog timer is disabled, the WDT timer will have the same
manner as in the enable-mode except that the timeout
signal will not generate a chip reset. So in the watchdog
timer disable mode, the WDT timer counter can be read
out and can be cleared. This function is used for the ap-
plication program to access the WDT frequency to get
the temperature coefficient for analog component ad-
justment. The WDT oscillator needs to be disabled/en-
abled by the special function registers(WDTC
:WDTOSC), for power saving reasons.
There are 2 registers related to the WDT function,
WDTC and WDTD. The WDTC register can control the
WDT oscillator enable/disable and the WDT power
source. WDTD is the WDT counter readout register.
WDTPWR can be used to choose the WDT power
source, the default source is VOCHP. The main purpose
of the regulator is to be used for the WDT Tempera-
ture-coefficient adjustment. In this case, the application
program should enable the regulator before switching to
the Regulator source. The WDTOSC can be used to en-
able or disable the WDT OSC (12kHz). If the application
does not use the WDT OSC, then it needs to disable it in
order to save power. When WDTOSC is disabled, then it
is actually turned off, regardless of the IRCC setting.
Function
Function
13
to 2
16
division ration range.
HT46R71D-1
May 14, 2007