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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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ATMEGA1280 датащи(PDF) 27 Page - ATMEL Corporation |
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ATMEGA1280 датащи(HTML) 27 Page - ATMEL Corporation |
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27 / 407 page  27 ATmega640/1280/1281/2560/2561 2549A–AVR–03/05 The next code examples show assembly and C functions for reading the EEPROM. The examples assume that interrupts are controlled so that no interrupts will occur during execution of these functions. Note: 1. See “About Code Examples” on page 8. Preventing EEPROM Corruption During periods of low V CC, the EEPROM data can be corrupted because the supply volt- age 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. Secondly, 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 completed provided that the power supply voltage is sufficient. Assembly Code Example(1) EEPROM_read: ; Wait for completion of previous write sbic EECR,EEPE rjmp EEPROM_read ; Set up address (r18:r17) in address register out EEARH, r18 out EEARL, r17 ; Start eeprom read by writing EERE sbi EECR,EERE ; Read data from Data Register in r16,EEDR ret C Code Example(1) unsigned char EEPROM_read(unsigned int uiAddress) { /* Wait for completion of previous write */ while(EECR & (1<<EEPE)) ; /* Set up address register */ EEAR = uiAddress; /* Start eeprom read by writing EERE */ EECR |= (1<<EERE); /* Return data from Data Register */ return EEDR; } |
Аналогичный номер детали - ATMEGA1280 |
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Аналогичное описание - ATMEGA1280 |
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