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| 型号： | EP20K100BC196-2 |
| 厂商： | ALTERA CORP |
| 元件分类： | PLD |
| 英文描述： | LOADABLE PLD, PBGA196 |
| 文件页数： | 48/68页 |
| 文件大小： | 975K |
| 代理商： | EP20K100BC196-2 |
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52
4317K–AVR–03/2013
AT90PWM2/3/2B/3B
9.2
Watchdog Timer
AT90PWM2/2B/3/3B has an Enhanced Watchdog Timer (WDT). The main features are:
Clocked from separate On-chip Oscillator
3 Operating modes
– Interrupt
– System Reset
– Interrupt and System Reset
Selectable Time-out period from 16ms to 8s
Possible Hardware fuse Watchdog always on (WDTON) for fail-safe mode
Figure 9-7.
Watchdog Timer
The Watchdog Timer (WDT) is a timer counting cycles of a separate on-chip 128 kHz oscillator.
The WDT gives an interrupt or a system reset when the counter reaches a given time-out value.
In normal operation mode, it is required that the system uses the WDR - Watchdog Timer Reset
- instruction to restart the counter before the time-out value is reached. If the system doesn't
restart the counter, an interrupt or system reset will be issued.
In Interrupt mode, the WDT gives an interrupt when the timer expires. This interrupt can be used
to wake the device from sleep-modes, and also as a general system timer. One example is to
limit the maximum time allowed for certain operations, giving an interrupt when the operation
has run longer than expected. In System Reset mode, the WDT gives a reset when the timer
expires. This is typically used to prevent system hang-up in case of runaway code. The third
mode, Interrupt and System Reset mode, combines the other two modes by first giving an inter-
rupt and then switch to System Reset mode. This mode will for instance allow a safe shutdown
by saving critical parameters before a system reset.
The “Watchdog Timer Always On” (WDTON) fuse, if programmed, will force the Watchdog Timer
to System Reset mode. With the fuse programmed the System Reset mode bit (WDE) and Inter-
rupt mode bit (WDIE) are locked to 1 and 0 respectively. To further ensure program security,
alterations to the Watchdog set-up must follow timed sequences. The sequence for clearing
WDE and changing time-out configuration is as follows:
1.
In the same operation, write a logic one to the Watchdog change enable bit (WDCE) and
WDE. A logic one must be written to WDE regardless of the previous value of the WDE
bit.
2.
Within the next four clock cycles, write the WDE and Watchdog prescaler bits (WDP) as
desired, but with the WDCE bit cleared. This must be done in one operation.
128 KHz
OSCILLATOR
MCU RESET
INTERRUPT
WDIE
WDIF
OSC/2K
OSC/4K
OSC/8K
WDP3
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相关代理商/技术参数 |
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| EP20K100BC356-1 | 功能描述:FPGA - 现场可编程门阵列 CPLD - APEX 20K 416 Macro 252 IOs RoHS:否 制造商:Altera Corporation 系列:Cyclone V E 栅极数量: 逻辑块数量:943 内嵌式块RAM - EBR:1956 kbit 输入/输出端数量:128 最大工作频率:800 MHz 工作电源电压:1.1 V 最大工作温度:+ 70 C 安装风格:SMD/SMT 封装 / 箱体:FBGA-256 |
| EP20K100BC356-1ES | 制造商:未知厂家 制造商全称:未知厂家 功能描述:FPGA |
| EP20K100BC356-1V | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| EP20K100BC356-2 | 功能描述:FPGA - 现场可编程门阵列 CPLD - APEX 20K 416 Macro 252 IOs RoHS:否 制造商:Altera Corporation 系列:Cyclone V E 栅极数量: 逻辑块数量:943 内嵌式块RAM - EBR:1956 kbit 输入/输出端数量:128 最大工作频率:800 MHz 工作电源电压:1.1 V 最大工作温度:+ 70 C 安装风格:SMD/SMT 封装 / 箱体:FBGA-256 |
| EP20K100BC356-2ES | 制造商:未知厂家 制造商全称:未知厂家 功能描述:FPGA |
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