
16
ATtiny25/45/85 [DATASHEET]
2586Q–AVR–08/2013
Figure 5-2.
Data Memory Map
5.2.1
Data Memory Access Times
This section describes the general access timing concepts for internal memory access. The internal data SRAM
access is performed in two clk
Figure 5-3.
On-chip Data SRAM Access Cycles
5.3
EEPROM Data Memory
The ATtiny25/45/85 contains 128/256/512 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 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. For details see
5.3.1
EEPROM Read/Write Access
The EEPROM Access Registers are accessible in the I/O space.
The write access times for the EEPROM are given in
Table 5-1 on page 21. 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
CC 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 mini-
problems in these situations.
In order to prevent unintentional EEPROM writes, a specific write procedure must be followed. Refer to
“Atomic32 Registers
64 I/O Registers
Internal SRAM
(128/256/512 x 8)
0x0000 - 0x001F
0x0020 - 0x005F
0x0DF/0x015F/0x025F
0x0060
Data Memory
clk
WR
RD
Data
Address
Address valid
T1
T2
T3
Compute Address
Read
Wr
ite
CPU
Memory Access Instruction
Next Instruction