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ATMEGA8515 Datasheet(PDF) 21 Page - ATMEL Corporation |
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ATMEGA8515 Datasheet(HTML) 21 Page - ATMEL Corporation |
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21 / 257 page  21 ATmega8515(L) 2512K–AVR–01/10 Caution: An interrupt between step 5 and step 6 will make the write cycle fail, since the EEPROM Master Write Enable will time-out. If an interrupt routine accessing the EEPROM is interrupting another EEPROM access, the EEAR or EEDR Register will be modified, causing the interrupted EEPROM access to fail. It is recommended to have the Global Interrupt Flag cleared during all the steps to avoid these problems. When the write access time has elapsed, the EEWE bit is cleared by hardware. The user software can poll this bit and wait for a zero before writing the next byte. When EEWE has been set, the CPU is halted for two cycles before the next instruction is executed. • Bit 0 – EERE: EEPROM Read Enable The EEPROM Read Enable Signal EERE is the read strobe to the EEPROM. When the correct address is set up in the EEAR Register, the EERE bit must be written to a logic one to trigger the EEPROM read. The EEPROM read access takes one instruction, and the requested data is available immediately. When the EEPROM is read, the CPU is halted for four cycles before the next instruction is executed. The user should poll the EEWE bit before starting the read operation. If a write operation is in progress, it is neither possible to read the EEPROM, nor to change the EEAR Register. The calibrated Oscillator is used to time the EEPROM accesses. Table 1 lists the typical programming time for EEPROM access from the CPU. Note: 1. Uses 1 MHz clock, independent of CKSEL Fuse settings. The following code examples show one assembly and one C function for writing to the EEPROM. The examples assume that interrupts are controlled (e.g., by disabling inter- rupts globally) so that no interrupts will occur during execution of these functions. The examples also assume that no Flash Boot Loader is present in the software. If such code is present, the EEPROM write function must also wait for any ongoing SPM com- mand to finish. Table 1. EEPROM Programming Time Symbol Number of Calibrated RC Oscillator Cycles(1) Typ Programming Time EEPROM Write (from CPU) 8448 8.5 ms |
Similar Part No. - ATMEGA8515_10 |
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Similar Description - ATMEGA8515_10 |
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