Datasheet

178
8246B–AVR–09/11
ATtiny2313A/4313
20. Lock Bits, Fuse Bits and Device Signature
20.1 Lock Bits
ATtiny2313A/4313 provides the program and data memory lock bits listed in Table 20-1.
Notes: 1. “1” means unprogrammed, “0” means programmed.
Lock bits can be left unprogrammed (“1”) or can be programmed (“0”) to obtain the additional
features listed in Table 20-2.
Notes: 1. “1” means unprogrammed, “0” means programmed.
2. Program fuse bits before programming LB1 and LB2.
When programming the lock bits, the mode of protection can be increased, only. Writing the
same, or lower, mode of protection automatically results in maximum protection.
Lock bits can be erased to “1” with the Chip Erase command, only.
The ATtiny2313A/4313 has no separate boot loader section. The SPM instruction is enabled for
the whole Flash if the SELFPRGEN fuse is programmed (“0”), otherwise it is disabled.
Table 20-1. Lock Bit Byte
Lock Bit Byte Bit No Description See Default Value
(1)
– 7 – 1 (unprogrammed)
– 6 – 1 (unprogrammed)
– 5 – 1 (unprogrammed)
– 4 – 1 (unprogrammed)
– 3 – 1 (unprogrammed)
– 2 – 1 (unprogrammed)
LB2 1
Lock bit Below
1 (unprogrammed)
LB1 0 1 (unprogrammed)
Table 20-2. Lock Bit Protection Modes.
Lock Bits
(1)
Mode of ProtectionLB2 LB1
1 1 No memory lock features enabled
10
Further programming of Flash and EEPROM is disabled in parallel and serial
programming mode. Fuse bits are locked in both serial and parallel
programming mode
(2)
01Reserved
00
Further reading and programming of Flash and EEPROM is disabled in
parallel and serial programming mode. Fuse bits are locked in both serial and
parallel programming mode
(2)