Rainbow-electronics ATmega8HVD Manuel d'utilisateur télécharger pdf (Page 129)

129

8052B–AVR–09/08

ATmega4HVD/8HVD

24. Memory Programming

24.1 Program And Data Memory Lock Bits

The ATmega4HVD/8HVD provides two Lock bits which can be left unprogrammed (“1”) or can

be programmed (“0”) to obtain the additional features listed in Table 24-2. The Lock bits can

only be erased to “1” with the Chip Erase command.

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

Notes: 1. Program the Fuse bits and Boot Lock bits before programming the LB1 and LB2.

2. “1” means unprogrammed, “0” means programmed

24.2 Fuse Bits

The ATmega4HVD/8HVD has two Fuse bytes. Table 24-4 and Table 24-3 describe briefly the

functionality of all the fuses and how they are mapped into the Fuse byte. Note that the fuses

are read as logical zero, “0”, if they are programmed.

24.2.1 High Byte

Table 24-1. Lock Bit Byte

(1)

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 24-2. Lock Bit Protection Modes

(1)(2)

Memory Lock Bits Protection Type

LB Mode LB2 LB1

1 1 1 No memory lock features enabled.

210

The Fuse bits are locked and further programming of the Flash

and EEPROM is disabled programming mode.

(1)

300

The Fuse bits are locked and further programming and

verification of the Flash and EEPROM is disabled

programming mode.

(1)

Table 24-3. Fuse High Byte

Bit No Fuse High Byte Description Default Value

7:2 – – 1 (unprogrammed)

1 OSCSEL1 Oscillator Select 1 1 (unprogrammed)

0 OSCSEL0 Oscillator Select 0 0 (programmed)

1 2 ... 124 125 126 127 128 129 130 131 132 133 134 ... 167 168

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