Rainbow-electronics ATmega8515L Manuel d'utilisateur télécharger pdf (Page 19)

ATmega8515(L)

2512A–AVR–04/02

• Bit 0 – EERE: EEPROM Read Enable

The EEPROM ReadEnable SignalEERE is the readstrobetothe EEPROM. When the

correctaddress isset up in the EEAR Register, the EEREbit must be written to a logic

one to trigger the EEPROM read.The EEPROM read access takes one instruction, and

the requesteddata is availableimmediately. When the EEPROM isread, the CPU is

haltedforfourcyclesbeforethenextinstruction is executed.

Theusershould poll the EEWE bit before starting the read operation. If a write operation

is in progress, it is neitherpossibletoread the EEPROM, nor to change the EEAR

The calibratedOscillator is used to time the EEPROM accesses.Table1lists thetypical

programming time forEEPROM access from the CPU.

Note: 1. Uses 1 MHz clock, independent of CKSEL Fuse settings.

Table 1. EEPROM Programming Time

Symbol

Number of Calibrated RC

Oscillator Cycles

(1)

Typ Programming Time

EEPROM Write (from CPU) 8448 8.5 ms

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 222 223

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Rainbow-electronics ATmega8515L Manuel d'utilisateur Page 19