attiny13-20ss ATMEL Corporation, attiny13-20ss Datasheet - Page 15

• Manufacturer Part Number: attiny13-20ss
• Description: 8-bit Microcontroller With 1k Bytes In-system Programmable Flash - Atmel Corporation
• Manufacturer: ATMEL Corporation

EEPROM Data Memory
EEPROM Read/Write Access
EEPROM Address Register –
EEARL
EEPROM Data Register –
EEDR
2535G–AVR–01/07
The ATtiny13 contains 64 bytes of data EEPROM memory. It is organized as a separate
data space, in which single bytes can be read and written. The EEPROM has an endur-
ance 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 Serial data downloading to the EEPROM, see page 107.
The EEPROM Access Registers are accessible in the I/O space.
The write access times for the EEPROM are given in Table 1. A self-timing function,
however, lets the user software detect when the next byte can be written. If the user
code contains instructions that write the EEPROM, some precautions must be taken. In
heavily filtered power supplies, V
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
19 for details on how to avoid problems in these situations.
In order to prevent unintentional EEPROM writes, a specific write procedure must be fol-
lowed. Refer to “Atomic Byte Programming” on page 17 and “Split Byte Programming”
on page 17 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.
• Bits 7..6 – Res: Reserved Bits
These bits are reserved bits in the ATtiny13 and will always read as zero.
• Bits 5..0 – EEAR5..0: EEPROM Address
The EEPROM Address Register – EEARL – specifies the EEPROM address in the 64
bytes EEPROM space. The EEPROM data bytes are addressed linearly between 0 and
63. The initial value of EEARL is undefined. A proper value must be written before the
EEPROM may be accessed.
• Bits 7..0 – EEDR7..0: EEPROM Data
For the EEPROM write operation the EEDR Register contains the data to be written to
the EEPROM in the address given by the EEARL Register. For the EEPROM read oper-
ation, the EEDR contains the data read out from the EEPROM at the address given by
EEARL.
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
EEDR7
R/W
R
X
7
–
0
7
EEDR6
R/W
R
X
6
–
0
6
EEAR5
EEDR5
R/W
R/W
X
X
5
5
CC
is likely to rise or fall slowly on Power-up/down. This
EEAR4
EEDR4
R/W
R/W
4
X
4
X
EEAR3
EEDR3
R/W
R/W
3
X
3
X
EEAR2
EEDR2
R/W
R/W
X
X
2
2
EEDR1
EEAR1
R/W
R/W
X
X
1
1
EEAR0
EEDR0
R/W
R/W
X
X
0
0
EEARL
EEDR
15