Datasheet

168
8197C–AVR–05/11
ATtiny261A/461A/861A
18. Memory Programming
This section describes the different methods for programming ATtiny261A/461A/861A
memories.
18.1 Program And Data Memory Lock Bits
The device provides two lock bits which can be left unprogrammed (“1”) or can be programmed
(“0”) to obtain the additional security listed in Table 18-2. The lock bits can only be erased to “1”
with the Chip Erase command.
The device has no separate boot loader section. The SPM instruction is enabled for the whole
Flash, if the SELFPROGEN fuse is programmed (“0”), otherwise it is disabled.
Program memory can be read out via the debugWIRE interface when the DWEN fuse is pro-
grammed, even if lock bits are set. Thus, when lock bit security is required, debugWIRE should
always be disabled by clearing the DWEN fuse.
Note: “1” means unprogrammed, “0” means programmed.
Notes: 1. Program fuse bits before programming LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed.
Lock bits can also be read by device firmware. See section “Reading Fuse and Lock Bits from
Software” on page 165.
Table 18-1. Lock Bit Byte
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 18-2. Lock Bit Protection Modes.
Memory Lock Bits
(1) (2)
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)
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)