attiny25v ATMEL Corporation, attiny25v Datasheet - Page 151

• Manufacturer Part Number: attiny25v
• Description: Microcontroller With 2/4/8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

20. Memory Programming
20.1
2586K–AVR–01/08
Program And Data Memory Lock Bits
This section describes the different methods for Programming the ATtiny25/45/85 memories.
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
“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).
Table 20-1.
Note:
Table 20-2.
Notes:
Lock bits can also be read by device firmware. See section
Data from Software” on page
LB2
LB1
LB Mode
1
2
3
Lock Bit
1. “1” means unprogrammed, “0” means programmed
1. Program the Fuse bits before programming the LB1 and LB2.
2. “1” means unprogrammed, “0” means programmed
Memory Lock Bits
Lock Bit Byte
Lock Bit Protection Modes
LB2
1
1
0
(1)
LB1
147.
1
0
0
Bit No
7
6
5
4
3
2
1
0
Protection Type
No memory lock features enabled.
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.
debugWire is disabled.
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)(2)
Description
–
–
–
–
–
–
Lock bit
Lock bit
(1)
Table
debugWire is disabled.
“Reading Lock, Fuse and Signature
20-2. Lock bits can be erased to
ATtiny25/45/85
Default Value
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
1 (unprogrammed)
(1)
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