ATtiny43U datasheet(139/182 Pages) ATMEL

139 / 182 page

139

8048B–AVR–03/09

19. Memory Programming

This section describes the different methods for Programming the ATtiny43U memories.

19.1

Program And Data Memory Lock Bits

The ATtiny43U 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 on page 139. 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. “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 the Fuse and Lock Bits

from Software” on page 135.

Table 19-1.

Lock Bit Byte

(1)

Lock Bit Byte

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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