ATTINY48-AUR 查看數據表（PDF） - Atmel Corporation
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ATTINY48-AUR Datasheet PDF : 298 Pages
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Figure 5-3. On-chip Data SRAM Access Cycles
T1
T2
T3
clk
CPU
Address
Data
WR
Data
RD
Compute Address
Address valid
Memory Access Instruction
Next Instruction
5.3 EEPROM Data Memory
ATtiny48/88 devices contain 64 bytes of data EEPROM memory, organized 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.
“Memory Programming” on page 187 contains a detailed description on EEPROM Programming
in SPI or Parallel Programming mode.
5.3.1
5.3.2
EEPROM Read/Write Access
The EEPROM Access Registers are located in I/O space.
The write access time for the EEPROM is given in Table 5-2. A self-timing function, however,
lets the user software detect when the next byte can be written. If the user code contains instruc-
tions that write the EEPROM, some precautions must be taken. In heavily filtered power
supplies, VCC 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 “Atomic Byte Programming” on page 18 and “Split Byte Programming” on page 19 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.
Atomic Byte Programming
The simplest programming method is called Atomic Byte Programming. When writing a byte to
the EEPROM, the user must write the address into register EEAR and data into register EEDR.
18 ATtiny48/88
8008F–AVR–06/10
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