Datasheet

163
7701F–AVR–10/12
Atmel ATtiny24/44/84 [Preliminary]
21. Memory Programming
This section describes the different methods for programming the Atmel
®
ATtiny24/44/84
memories.
21.1 Program And Data Memory Lock Bits
The ATtiny24/44/84 provides two lock bits which can be left unprogrammed (set to one) or can
be programmed (set to zero) to obtain the additional security listed in Table 21-2 on page 163.
The lock bits can only be erased to one with the chip erase command.
Program memory can be read 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 LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed
Table 21-1. Lock Bit Byte
(1)
Lock Bit Byte 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 21-2. 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.