參數(shù)資料
型號: SC16C654BIB64,151
廠商: NXP Semiconductors
文件頁數(shù): 14/58頁
文件大?。?/td> 0K
描述: IC UART QUAD W/FIFO 64-LQFP
標(biāo)準(zhǔn)包裝: 160
特點(diǎn): 故障啟動位檢測
通道數(shù): 4,QUART
FIFO's: 64 字節(jié)
電源電壓: 2.5V,3.3V,5V
帶自動流量控制功能:
帶IrDA 編碼器/解碼器:
帶故障啟動位檢測功能:
帶調(diào)制解調(diào)器控制功能:
帶CMOS:
安裝類型: 表面貼裝
封裝/外殼: 64-LQFP
供應(yīng)商設(shè)備封裝: 64-LQFP(10x10)
包裝: 托盤
其它名稱: 568-3647
568-3647-ND
568-8273
935274936151
SC16C654BIB64-S
21
7674F–AVR–09/09
ATmega164P/324P/644P
6.4
EEPROM Data Memory
The ATmega164P/324P/644P contains 512B/1K/2K bytes of data EEPROM memory. It is orga-
nized as a separate data space, in which single bytes can be read and written. The EEPROM
has an endurance of at least 100,000 write/erase cycles. The access between the EEPROM and
the CPU is described in the following, specifying the EEPROM Address Registers, the EEPROM
Data Register, and the EEPROM Control Register.
For a detailed description of SPI, JTAG and Parallel data downloading to the EEPROM, see
page 311, page 315, and page 300 respectively.
6.4.1
EEPROM Read/Write Access
The EEPROM Access Registers are accessible in the I/O space. See “Register Description” on
page 23 for details.
The write access time for the EEPROM is given in Table 6-2 on page 25. A self-timing function,
however, lets the user software detect when the next byte can be written. If the user code con-
tains instructions that write the EEPROM, some precautions must be taken. In heavily filtered
power supplies, V
CC is likely to rise or fall slowly on power-up/down. This causes the device for
some period of time to run at a voltage lower than specified as minimum for the clock frequency
used. See “Preventing EEPROM Corruption” on page 21. for details on how to avoid problems in
these situations.
In order to prevent unintentional EEPROM writes, a specific write procedure must be followed.
Refer to the description of the EEPROM Control Register for details on this.
When the EEPROM is read, the CPU is halted for four clock cycles before the next instruction is
executed. When the EEPROM is written, the CPU is halted for two clock cycles before the next
instruction is executed.
6.4.2
Preventing EEPROM Corruption
During periods of low V
CC, the EEPROM data can be corrupted because the supply voltage is
too low for the CPU and the EEPROM to operate properly. These issues are the same as for
board level systems using EEPROM, and the same design solutions should be applied.
An EEPROM data corruption can be caused by two situations when the voltage is too low. First,
a regular write sequence to the EEPROM requires a minimum voltage to operate correctly. Sec-
ondly, the CPU itself can execute instructions incorrectly, if the supply voltage is too low.
EEPROM data corruption can easily be avoided by following this design recommendation:
Keep the AVR RESET active (low) during periods of insufficient power supply voltage. This can
be done by enabling the internal Brown-out Detector (BOD). If the detection level of the internal
BOD does not match the needed detection level, an external low V
CC reset Protection circuit can
be used. If a reset occurs while a write operation is in progress, the write operation will be com-
pleted provided that the power supply voltage is sufficient.
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