ATtiny44 datasheet(159/236 Pages) ATMEL

159 / 236 page

159

8006H–AVR–10/09

ATtiny24/44/84

19. Memory Programming

This section describes the different methods for programming ATtiny24/44/84 memories.

19.1

Program And Data Memory Lock Bits

The ATtiny24/44/84 provides two lock bits which can be left unprogrammed (“1”) or can be pro-

grammed (“0”) to obtain the additional security listed in Table 19-2. 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 Lock, Fuse and Signature

Data from Software” on page 155.

Table 19-1.

Lock Bit Byte

Lock Bit

Bit No

Description

Default Value

–

1 (unprogrammed)

–

1 (unprogrammed)

–

1 (unprogrammed)

–

1 (unprogrammed)

–

1 (unprogrammed)

–

1 (unprogrammed)

LB2

Lock bit

1 (unprogrammed)

LB1

Lock bit

1 (unprogrammed)

Table 19-2.

Lock Bit Protection Modes.

Memory Lock Bits

(1) (2)

Protection Type

LB Mode

LB2

LB1

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.

(1)

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) debugWire is disabled.

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