ATmega88 datasheet(278/340 Pages) ATMEL

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278

7530H–AVR–02/09

ATmega48/88/168 Automotive

Note:

1. Z15:Z14: always ignored

Z0: should be zero for all SPM commands, byte select for the LPM instruction.

See “Addressing the Flash During Self-Programming” on page 269 for details about the use of

Z-pointer during Self-Programming.

25. Memory Programming

25.1

Program And Data Memory Lock Bits

The ATmega88/168 provides six Lock bits which can be left unprogrammed (“1”) or can be pro-

grammed (“0”) to obtain the additional features listed in Table 25-2. The Lock bits can only be

erased to “1” with the Chip Erase command.The ATmega48 has no separate Boot Loader sec-

tion. The SPM instruction is enabled for the whole Flash if the SELFPRGEN fuse is programmed

(“0”), otherwise it is disabled.

Notes:

1. “1” means unprogrammed, “0” means programmed

2. Only on ATmega88/168.

PAGEMSB

Most significant bit which is used to address

the words within one page (64 words in a page

requires 6 bits PC [5:0])

ZPCMSB

Z13

Bit in Z-register that is mapped to PCMSB. Because

Z0 is not used, the ZPCMSB equals PCMSB + 1.

ZPAGEMSB

Bit in Z-register that is mapped to PAGEMSB.

Because Z0 is not used, the ZPAGEMSB equals

PAGEMSB + 1.

PCPAGE

PC[12:6]

Z13:Z7

Program counter page address: Page select, for

page erase and page write

PCWORD

PC[5:0]

Z6:Z1

Program counter word address: Word select, for

filling temporary buffer (must be zero during page

write operation)

Table 24-11. Explanation of Different Variables used in Figure 24-3 and the Mapping to the

Z-pointer, ATmega168

Variable

Corresponding

Z-value(1)

Description

Table 25-1.

Lock Bit Byte

(1)

Lock Bit Byte

Bit No

Description

Default Value

–

1 (unprogrammed)

–

1 (unprogrammed)

BLB12()

Boot Lock bit

1 (unprogrammed)

BLB11()

Boot Lock bit

1 (unprogrammed)

BLB02()

Boot Lock bit

1 (unprogrammed)

BLB01()

Boot Lock bit

1 (unprogrammed)

LB2

Lock bit

1 (unprogrammed)

LB1

Lock bit

1 (unprogrammed)

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