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參數(shù)資料
| 型號(hào)： | AT43USB351M-AC |
| 廠商： | ATMEL CORP |
| 元件分類： | 微控制器/微處理器 |
| 英文描述： | Full-speed/Low-speed USB Microcontroller with ADC and PWM |
| 中文描述： | 8-BIT, MROM, 24 MHz, RISC MICROCONTROLLER, PQFP48 |
| 封裝： | 7 X 7 MM, 1.40 MM HEIGHT, 0.50 MM PITCH, PLASTIC, MS-026BBC, LQFP-48 |
| 文件頁數(shù)： | 97/101頁 |
| 文件大?。?/td> | 624K |
| 代理商： | AT43USB351M-AC |
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97
AT43USB351M
3302E–USB–7/04
Errata Sheet
Errata (All Date Codes): Missed Watchdog Timer Reset
Problem
There is a synchronization problem between the watchdog clock and the AVR clock. Even
though the clock inputs to both the watchdog timer and the AVR core are generated through
the same crystal, the two clock sources are not going through the same PLL. The AVR is
clocked at 12 MHz and the watchdog timer is clocked at 1MHz. The WDR (Watchdog Reset)
instruction is a one-clock-cycle instruction. As such, when a watchdog timer reset occurs due
to a WDR, the watchdog timer may miss the reset. This happens frequently if the AVR is
clocked much faster than the watchdog timer.
Fix/Workaround
A workaround is to invoke the WDR repetitively to ensure that the watchdog timer will be able
to receive the reset signal. If the AVR runs at 12 MHz, the WDR command must be invoked
fourteen times back to back.
The following is the sample code for resetting and arming the watchdog timer, assuming the
AVR is running at 12 MHz:
asm ( "ldi r16,15\n WDR\n WDR\n WDR\n WDR\n WDR\n WDR\n WDR\n WDR\n WDR\n
WDR\n WDR\n WDR\n WDR\n out 0x21,r16 " );
To disarm and disable the watchdog, do the following:
asm ( "ldi r16,0x18\nldi r17,0x10\n\n out 0x21,r16\n out 0x21,r17 " );
Please note that if the AVR runs at 24 MHz, the WDR should be invoked twenty-six times.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AT43USB353M | 制造商:ATMEL 制造商全稱:ATMEL Corporation 功能描述:Missed Watchdog Timer Reset |
| AT43USB353M_03 | 制造商:ATMEL 制造商全稱:ATMEL Corporation 功能描述:Low Cost USB Microcontroller with Hub, ADC and PWM |
| AT43USB353M_04 | 制造商:ATMEL 制造商全稱:ATMEL Corporation 功能描述:Low Cost Full-speed USB Microcontroller with Embedded Hub, ADC and PWM |
| AT43USB353M-AC | 制造商:ATMEL 制造商全稱:ATMEL Corporation 功能描述:Low Cost Full-speed USB Microcontroller with Embedded Hub, ADC and PWM |
| AT43USB355 | 制造商:ATMEL 制造商全稱:ATMEL Corporation 功能描述:Missed Watchdog Timer Reset |
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