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參數(shù)資料
| 型號： | HT48RA3 |
| 廠商： | Holtek Semiconductor Inc. |
| 英文描述： | 8-Bit Remote Type OTP MCU |
| 中文描述： | 8位單片機的遠程型檢察官辦公室 |
| 文件頁數(shù)： | 9/36頁 |
| 文件大?。?/td> | 245K |
| 代理商： | HT48RA3 |
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HT48RA3
Rev. 1.20
9
May 12, 2003
shift required for the oscillator, and no other external
components are demanded. Instead of a crystal, the
resonator can also be connected between OSC1 and
OSC2 to get a frequency reference, but two external ca-
pacitors in OSC1 and OSC2 are required.
The WDT oscillator is a free running on-chip RC oscilla-
tor, and no external components are required. Even if
the system enters the power down mode, the system
clock is stopped, but the WDT oscillator still works with a
period of approximately 90 s. The WDT oscillator can
be disabled by ROM code option to conserve power.
Watchdog Timer
WDT
The WDT clock source is implemented by a dedicated
RC oscillator (WDT oscillator), instruction clock (system
clock divided by 4), determines the ROM code option.
This timer is designed to prevent a software malfunction
or sequence from jumping to an unknown location with
unpredictable results. The Watchdog Timer can be dis-
abled by ROM code option. If the Watchdog Timer is dis-
abled, all the executions related to the WDT result in no
operation.
Once the internal WDT oscillator (RC oscillator with a
period of 90 s/3V normally) is selected, it is first divided
by 256 (8-stage) to get the nominal time-out period of
23ms/3V. This time-out period may vary with tempera-
tures, VDD and process variations. By invoking the
WDT prescaler, longer time-out periods can be realized.
Writing data to WS2, WS1, WS0 (bit 2,1,0 of the WDTS)
can give different time-out periods. If WS2, WS1, and
WS0 are all equal to 1, the division ratio is up to 1:128,
and the maximum time-out period is 2.9s/3V seconds. If
the WDT oscillator is disabled, the WDT clock may still
come from the instruction clock and operates in the
same manner except that in the HALT state the WDT
may stop counting and lose its protecting purpose. In
this situation the logic can only be restarted by external
logic. The high nibble and bit 3 of the WDTS are re-
served for user s defined flags, which can be used to in-
dicate some specified status.
If the device operates in a noisy environment, using the
on-chip RC oscillator (WDT OSC) is strongly recom-
mended, since the HALT will stop the system clock.
WS2
WS1
WS0
Division Ratio
0
0
0
1:1
0
0
1
1:2
0
1
0
1:4
0
1
1
1:8
1
0
0
1:16
1
0
1
1:32
1
1
0
1:64
1
1
1
1:128
WDTS register
The WDT overflow under normal operation will initialize
chip reset and set the status bit TO . But in the HALT
mode, the overflow will initialize a warm reset and only
the PC and SP are reset to zero. To clear the contents of
WDT (including the WDT prescaler), three methods are
adopted;externalreset(alowleveltoRES),softwarein-
structionanda HALT instruction.Thesoftwareinstruc-
tion include
CLR WDT
and the other set
CLR
WDT1 and CLR WDT2 . Of these two types of instruc-
tion, only one can be active depending on the ROM
code option
CLR WDT times selection option . If the
CLR WDT is selected (i.e. CLRWDT times equal one),
any execution of the CLR WDT instruction will clear
the WDT. In the case that
CLR WDT1
and
CLR
WDT2
these two instructions must be executed to clear the
WDT; otherwise, the WDT may reset the chip as a result
of time-out.
are chosen (i.e. CLRWDT times equal two),
Power Down Operation
HALT
The HALT mode is initialized by the HALT instruction
and results in the following...
The system oscillator will be turned off but the WDT
oscillator remains running (if the WDT oscillator is se-
lected).
The contents of the on chip RAM and registers remain
unchanged.
WDT and WDT prescaler will be cleared and re-
counted again (if the WDT clock is from the WDT os-
cillator).
All of the I/O ports maintain their original status.
The PD flag is set and the TO flag is cleared.
&
!
,
; 1
2 9 < # ! ,
!
+
,
/ 9 < # ! ,
!
2 9 ! 9 ,
+
, #
9
!
+
. +
'
" ! #
!
+
Watchdog Timer
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相關(guān)代理商/技術(shù)參數(shù) |
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| HT48RA3_07 | 制造商:HOLTEK 制造商全稱:Holtek Semiconductor Inc 功能描述:Remote Type 8-Bit MCU |
| HT48RA3_09 | 制造商:HOLTEK 制造商全稱:Holtek Semiconductor Inc 功能描述:HT48RA3/HT48CA3 |
| HT48RA5 | 制造商:HOLTEK 制造商全稱:Holtek Semiconductor Inc 功能描述:Remote Type 8-Bit MCU |
| HT48RA5_07 | 制造商:HOLTEK 制造商全稱:Holtek Semiconductor Inc 功能描述:Remote Type 8-Bit MCU |
| HT48RA5_09 | 制造商:HOLTEK 制造商全稱:Holtek Semiconductor Inc 功能描述:Remote Type 8-Bit MCU |
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