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參數(shù)資料
| 型號： | PCA84C922 |
| 廠商： | NXP Semiconductors N.V. |
| 英文描述： | Microcontrollers for universal infrared remote transmitter applications(應用于通用紅外線遙控傳送的微控制器) |
| 中文描述： | 對通用紅外遙控發(fā)射器應用微控制器（應用于通用紅外線遙控傳送的微控制器） |
| 文件頁數(shù)： | 19/36頁 |
| 文件大小： | 250K |
| 代理商： | PCA84C922 |
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1997 Oct 22
19
Philips Semiconductors
Product specification
Microcontrollers for universal infrared
remote transmitter applications
PCA84C922; PCA84C923
9
WATCHDOG TIMER (WDT)
The PCA84C92X contains a Watchdog Timer that
functions in the same manner as the Watchdog Timer
used in the PCA84CX22 range of microcontrollers.
The purpose of the Watchdog Timer is to reset the
microcontroller if it enters an erroneous processor state;
within a reasonable period of time. Erroneous processor
states can be caused by noise or RFI.
The Watchdog Timer consists of a 17-bit counter which is
clocked at a frequency of
1
30
f
osc
. During a Power-on-reset
the contents of the counter are cleared. The counter
contents are then incremented by ‘1’ every 30 cycles of the
oscillator clock. If the maximum count is exceeded, the
counter overflows and the microcontroller is reset. In order
to prevent a counter overflow and its resulting reset
operation, the user program must clear the contents of the
Watchdog Timer before its maximum count is reached.
During normal processing, the contents of the Watchdog
Timer are cleared by writing a logic 1 to the WRES bit in
Hardware Modulator Control Register (address 03H).
The maximum time period (t
p
) which the counter may run
and not cause a reset operation, is calculated as shown
below.
In the Idle mode the oscillator is still running and the
Watchdog Timer remains active. In the Stop mode
however, the oscillator is stopped and the operation of the
Watchdog Timer is halted but its contents are retained.
Therefore, it may be advisable for the user to clear the
contents of the Watchdog Timer before the Stop mode is
entered, in order to avoid an unexpected reset operation
after the device is woken-up.
t
p
osc
f
30
2
16
×
×
=
Fig.15 Block diagram of the Watchdog Timer.
handbook, full pagewidth
WRES
HMCTL register (address O3H)
PWM
HF
Rint
Lg
30
Power-on-reset
RESET
CLK
Q16
on-chip RESET
17-BIT COUNTER
fosc
MBE415
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| PCA84C922A | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Microcontrollers for universal infrared remote transmitter applications |
| PCA84C922AP | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Microcontrollers for universal infrared remote transmitter applications |
| PCA84C922AT | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Microcontrollers for universal infrared remote transmitter applications |
| PCA84C922C | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Microcontrollers for universal infrared remote transmitter applications |
| PCA84C922CT | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Microcontrollers for universal infrared remote transmitter applications |
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