- 您現在的位置：買賣IC網 > PDF目錄363901 > W79E802A (WINBOND ELECTRONICS CORP) 8-BIT MICROCONTROLLER PDF資料下載
參數資料
| 型號： | W79E802A |
| 廠商： | WINBOND ELECTRONICS CORP |
| 元件分類： | 8位微控制器 |
| 英文描述： | 8-BIT MICROCONTROLLER |
| 中文描述： | 8位微控制器 |
| 文件頁數： | 71/115頁 |
| 文件大小： | 1456K |
| 代理商： | W79E802A |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁第31頁第32頁第33頁第34頁第35頁第36頁第37頁第38頁第39頁第40頁第41頁第42頁第43頁第44頁第45頁第46頁第47頁第48頁第49頁第50頁第51頁第52頁第53頁第54頁第55頁第56頁第57頁第58頁第59頁第60頁第61頁第62頁第63頁第64頁第65頁第66頁第67頁第68頁第69頁第70頁當前第71頁第72頁第73頁第74頁第75頁第76頁第77頁第78頁第79頁第80頁第81頁第82頁第83頁第84頁第85頁第86頁第87頁第88頁第89頁第90頁第91頁第92頁第93頁第94頁第95頁第96頁第97頁第98頁第99頁第100頁第101頁第102頁第103頁第104頁第105頁第106頁第107頁第108頁第109頁第110頁第111頁第112頁第113頁第114頁第115頁
W79E804A/803A/802A
Publication Release Date: July 16, 2007
- 71 -
Revision A2
15. WATCHDOG TIMER
The Watchdog Timer is a free-running Timer which can be programmed by the user to serve as a
system monitor, a time-base generator or an event timer. It is basically a set of dividers that divide the
system clock. The divider output is selectable and determines the time-out interval. When the time-out
occurs a flag is set, which can cause an interrupt if enabled, and a system reset can also be caused if
it is enabled. The interrupt will occur if the individual interrupt enable and the global enable are set.
The interrupt and reset functions are independent of each other and may be used separately or
together depending on the user’s software.
Figure
15-1: Watchdog Timer
The Watchdog Timer should first be restarted by using WDCLR. This ensures that the timer starts
from a known state. The WDCLR bit is used to restart the Watchdog Timer. This bit is self clearing, i.e.
after writing a 1 to this bit the software will automatically clear it. The Watchdog Timer will now count
clock cycles. The time-out interval is selected by the two bits WD1 and WD0 (WDCON.5 and
WDCON.4). When the selected time-out occurs, the Watchdog interrupt flag WDIF (WDCON.3) is set.
After the time-out has occurred, the Watchdog Timer waits for an additional 512 clock cycles. If the
Watchdog Reset EWRST (WDCON.1) is enabled, then 512 clocks after the time-out, if there is no
WDCLR, a system reset due to Watchdog Timer will occur. This will last for two machine cycles, and
the Watchdog Timer reset flag WTRF (WDCON.2) will be set. This indicates to the software that the
Watchdog was the cause of the reset.
When used as a simple timer, the reset and interrupt functions are disabled. The timer will set the
WDIF flag each time the timer completes the selected time interval. The WDIF flag is polled to detect a
time-out and the WDCLR allows software to restart the timer. The Watchdog Timer can also be used
as a very long timer. The interrupt feature is enabled in this case. Every time the time-out occurs an
interrupt will occur if the global interrupt enable EA is set.
The main use of the Watchdog Timer is as a system monitor. This is important in real-time control
applications. In case of some power glitches or electro-magnetic interference, the processor may
begin to execute errant code. If this is left unchecked the entire system may crash. Using the
watchdog timer interrupt during software development will allow the user to select ideal watchdog
reset locations. The code is first written without the watchdog interrupt or reset. Then the Watchdog
interrupt is enabled to identify code locations where interrupt occurs. The user can now insert
instructions to reset the Watchdog Timer, which will allow the code to run without any Watchdog Timer
interrupts. Now the Watchdog Timer reset is enabled and the Watchdog interrupt may be disabled. If
相關PDF資料 |
PDF描述 |
|---|---|
| W79E802ADG | 8-BIT MICROCONTROLLER |
| W79E802ASG | 8-BIT MICROCONTROLLER |
| W79E803 | 8-BIT MICROCONTROLLER |
| W79E803A | 8-BIT MICROCONTROLLER |
| W79E803ADG | 8-BIT MICROCONTROLLER |
相關代理商/技術參數 |
參數描述 |
|---|---|
| W79E802ADG | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W79E802ASG | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W79E803 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W79E803A | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W79E803ADG | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
發布緊急采購，3分鐘左右您將得到回復。