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參數資料
| 型號： | W77E468F-40 |
| 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： | 62/84頁 |
| 文件大小： | 352K |
| 代理商： | W77E468F-40 |
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Preliminary W77E468
- 62 -
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 users software.
16
WD1,WD0
00
01
10
11
Interrupt
Reset
Enable Watchdog timer reset
EWT(WDCON.1)
Reset Watchdog
RWT (WDCON.0)
0
17
19
20
22
23
25
Time-out
selector
WDIF
WTRF
512 clock
delay
EWDI(EIE.4)
Clock Source
Mode input
div. by 4 osc/1
div. by 64 osc/16
div. by 1024 osc/256
Figure 19. Watchdog Timer
The Watchdog timer should first be restarted by using RWT. This ensures that the timer starts from a
known state. The RWT 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 (CKCON.7 and CKCON.6).
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. The software must
issue a RWT to reset the watchdog before the 512 clocks have elapsed. If the Watchdog Reset EWT
(WDCON.1) is enabled, then 512 clocks after the time-out, if there is no RWT, 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 RWT 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.
相關PDF資料 |
PDF描述 |
|---|---|
| W77E468 | 8 BIT MICROCONTROLLER |
| W77E516 | 8-BIT MICROCONTROLLER |
| W77E516-25 | 8-BIT MICROCONTROLLER |
| W77E516-40 | 8-BIT MICROCONTROLLER |
| W77E516F-25 | 8-BIT MICROCONTROLLER |
相關代理商/技術參數 |
參數描述 |
|---|---|
| W77E516 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W77E516-25 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W77E516-40 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W77E516A | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W77E516A40DL | 功能描述:IC MCU 8-BIT 64K FLASH 40-DIP RoHS:是 類別:集成電路 (IC) >> 嵌入式 - 微控制器， 系列:W77 標準包裝:250 系列:80C 核心處理器:8051 芯體尺寸:8-位 速度:16MHz 連通性:EBI/EMI，I²C，UART/USART 外圍設備:POR，PWM，WDT 輸入/輸出數:40 程序存儲器容量:- 程序存儲器類型:ROMless EEPROM 大小:- RAM 容量:256 x 8 電壓 - 電源 (Vcc/Vdd):4.5 V ~ 5.5 V 數據轉換器:A/D 8x10b 振蕩器型:內部 工作溫度:-40°C ~ 85°C 封裝/外殼:68-LCC（J 形引線） 包裝:帶卷 (TR) |
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