ATMEGA8535L_14 Datasheet, PDF (238/321 Pages) ATMEL Corporation – Nonvolatile Program and Data Memories

Fuse Bits
Table 97. Lock Bit Protection Modes⁽²⁾ (Continued)
Memory Lock Bits
Protection Type
1
1
1
No restrictions for SPM or LPM accessing the Boot Loader
section.
2
1
0
SPM is not allowed to write to the Boot Loader section.
SPM is not allowed to write to the Boot Loader section,
and LPM executing from the Application section is not
3
0
0
allowed to read from the Boot Loader section. If interrupt
vectors are placed in the Application section, interrupts
are disabled while executing from the Boot Loader section.
LPM executing from the Application section is not allowed
4
0
1
to read from the Boot Loader section. If interrupt vectors
are placed in the Application section, interrupts are
disabled while executing from the Boot Loader section.
Notes: 1. Program the Fuse bits before programming the Lock bits.
2. “1” means unprogrammed, “0” means programmed.
The ATmega8535 has two Fuse bytes. Table 98 and Table 99 describe briefly the func-
tionality of all the fuses and how they are mapped into the fuse bytes. Note that the
fuses are read as logical zero, “0”, if they are programmed.
Table 98. Fuse High Byte
Fuse High Byte
S8535C
WDTON
SPIEN⁽¹⁾
CKOPT⁽²⁾
EESAVE
BOOTSZ1
BOOTSZ0
BOOTRST
Bit No
7
6
Description
Select AT90S8535 compatibility
mode
WDT always on
5 Enable Serial Program and Data
Downloading
4 Oscillator options
3 EEPROM memory is preserved
through the Chip Erase
2 Select Boot Size (see Table 93 for
details)
1 Select Boot Size (see Table 93 for
details)
0 Select Reset Vector
Default Value
1 (unprogrammed)
1 (unprogrammed, WDT
enabled by WDTCR)
0 (programmed, SPI prog.
enabled)
1 (unprogrammed)
1 (unprogrammed,
EEPROM not preserved)
0 (programmed)⁽³⁾
0 (programmed)⁽³⁾
1 (unprogrammed)
Notes:
1. The SPIEN Fuse is not accessible in Serial Programming mode.
2. The CKOPT Fuse functionality depends on the setting of the CKSEL bits. See “Clock
Sources” on page 25. for details.
3. The default value of BOOTSZ1..0 results in maximum Boot Size. See Table 93 on
page 235.
238 ATmega8535(L)
2502K–AVR–10/06