Part may hang in reset
參數資料
型號: ATMEGA48-20AUR
廠商: Atmel
文件頁數: 17/36頁
文件大?。?/td> 0K
描述: IC AVR MCU 4K 20MHZ 32TQFP
產品培訓模塊: megaAVR Introduction
標準包裝: 2,000
系列: AVR® ATmega
核心處理器: AVR
芯體尺寸: 8-位
速度: 20MHz
連通性: I²C,SPI,UART/USART
外圍設備: 欠壓檢測/復位,POR,PWM,WDT
輸入/輸出數: 23
程序存儲器容量: 4KB(2K x 16)
程序存儲器類型: 閃存
EEPROM 大?。?/td> 256 x 8
RAM 容量: 512 x 8
電壓 - 電源 (Vcc/Vdd): 2.7 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: 32-TQFP
包裝: 帶卷 (TR)
其它名稱: ATMEGA48-20AUR-ND
ATMEGA48-20AURTR
24
2545TS–AVR–05/11
ATmega48/88/168
11.1.4
Rev A
Part may hang in reset
Wrong values read after erase only operation
Watchdog timer interrupt disabled
Start-up time with crystal oscillator is higher than expected
High power consumption in power-down with external clock
Asynchronous oscillator does not stop in power-down
Interrupts may be lost when writing the timer registers in the asynchronous timer
1.
Part may hang in reset
Some parts may get stuck in a reset state when a reset signal is applied when the internal
reset state-machine is in a specific state. The internal reset state-machine is in this state for
approximately 10ns immediately before the part wakes up after a reset, and in a 10ns win-
dow when altering the system clock prescaler. The problem is most often seen during In-
System Programming of the device. There are theoretical possibilities of this happening also
in run-mode. The following three cases can trigger the device to get stuck in a reset-state:
- Two succeeding resets are applied where the second reset occurs in the 10ns window
before the device is out of the reset-state caused by the first reset.
- A reset is applied in a 10ns window while the system clock prescaler value is updated by
software.
- Leaving SPI-programming mode generates an internal reset signal that can trigger this
case.
The two first cases can occur during normal operating mode, while the last case occurs only
during programming of the device.
Problem fix/workaround
The first case can be avoided during run-mode by ensuring that only one reset source is
active. If an external reset push button is used, the reset start-up time should be selected
such that the reset line is fully debounced during the start-up time.
The second case can be avoided by not using the system clock prescaler.
The third case occurs during In-System programming only. It is most frequently seen when
using the internal RC at maximum frequency.
If the device gets stuck in the reset-state, turn power off, then on again to get the device out
of this state.
2.
Wrong values read after erase only operation
At supply voltages below 2.7V, an EEPROM location that is erased by the Erase Only oper-
ation may read as programmed (0x00).
Problem fix/workaround
If it is necessary to read an EEPROM location after Erase Only, use an Atomic Write opera-
tion with 0xFF as data in order to erase a location. In any case, the Write Only operation can
be used as intended. Thus no special considerations are needed as long as the erased loca-
tion is not read before it is programmed.
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