Datasheet

151
2586N–AVR–04/11
ATtiny25/45/85
20. Memory Programming
This section describes the different methods for Programming the ATtiny25/45/85 memories.
20.1 Program And Data Memory Lock Bits
ATtiny25/45/85 provides two Lock bits which can be left unprogrammed (“1”) or can be pro-
grammed (“0”) to obtain the additional security listed in Table 20-2. Lock bits can be erased to
“1” with the Chip Erase command, only.
Program memory can be read out via the debugWIRE interface when the DWEN fuse is pro-
grammed, even if the Lock Bits are set. Thus, when Lock Bit security is required debugWIRE
should always be disabled (by clearing the DWEN fuse).
Note: 1. “1” means unprogrammed, “0” means programmed
Notes: 1. Program the Fuse bits before programming the LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed
Lock bits can also be read by device firmware. See section “Reading Lock, Fuse and Signature
Data from Software” on page 147.
Table 20-1. Lock Bit Byte
(1)
Lock Bit Bit No Description Default Value
7 – 1 (unprogrammed)
6 – 1 (unprogrammed)
5 – 1 (unprogrammed)
4 – 1 (unprogrammed)
3 – 1 (unprogrammed)
2 – 1 (unprogrammed)
LB2 1 Lock bit 1 (unprogrammed)
LB1 0 Lock bit 1 (unprogrammed)
Table 20-2. Lock Bit Protection Modes
(1)(2)
Memory Lock Bits Protection Type
LB Mode LB2 LB1
1 1 1 No memory lock features enabled.
210
Further programming of the Flash and EEPROM is disabled in
High-voltage and Serial Programming mode. The Fuse bits are
locked in both Serial and High-voltage Programming mode.
(1)
debugWire is disabled.
300
Further programming and verification of the Flash and EEPROM
is disabled in High-voltage and Serial Programming mode. The
Fuse bits are locked in both Serial and High-voltage
Programming mode.
(1)
debugWire is disabled.