atmega323l ATMEL Corporation, atmega323l Datasheet - Page 187

• Manufacturer Part Number: atmega323l
• Description: Atmega323 8-bit Avr Microcontroller With 32k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

Fuse Bits
1457G–AVR–09/03
Table 63. Lock Bit Protection Modes
Note:
The ATmega323 has 13 Fuse bits, divided in two groups. The Fuse High bits are
OCDEN, JTAGEN, SPIEN, EESAVE, BOOTSZ1..0, and BOOTRST, and the Fuse Low
bits are BODLEVEL, BODEN, and CKSEL3..0. All Fuses are accessible in Parallel Pro-
gramming mode and when programming via the JTAG interface. In Serial Programming
mode, all but the SPIEN Fuse is accessible.
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LB mode
When the OCDEN Fuse is programmed, the On-chip debug system is enabled if the
JTAGEN Fuse is programmed. If the JTAGEN Fuse is unprogrammed, the OCDEN
Fuse has no visible effect.Never ship a product with the OCDEN Fuse programmed.
Regardless of the setting of Lock bits and the JTAGEN Fuse, a programmed
OCDEN Fuse enables some parts of the clock system be running in all sleep
modes. This may increase the power consumption. Default value is unprogrammed
(“1”).
When the JTAGEN Fuse is programmed, the JTAG interface is enabled on port C
pins PC5..2. Default value is programmed (“0”).
If the JTAG interface is left unconnected, the JTAGEN fuse should if possible be
disabled. This to avoid static current at the TDO pin in the JTAG interface.
When the SPIEN Fuse is programmed (“0”), Serial Program and Data Downloading
are enabled. Default value is programmed (“0”). The SPIEN Fuse is not accessible
in SPI Serial Programming mode.
When EESAVE is programmed, the EEPROM Memory is preserved through the
Chip Erase cycle. Default value is unprogrammed (“1”). The EESAVE Fuse bit can
not be programmed if any of the Lock bits are programmed.
BOOTSZ1..0 select the size and start address of the Boot Flash section according
to Table on page 177. Default value is “11” (both unprogrammed).
When BOOTRST is programmed (“0”), the Reset Vector is set to the start address of
the Boot Flash section, as selected by the BOOTSZ Fuses according to Table 59 on
page 177. If the BOOTRST is unprogrammed (“1”), the Reset Vector is set to
address $0000. Default value is unprogrammed (“1”).
The BODLEVEL Fuse selects the Brown-out Detection Level and changes the Start-
up times, according to Table 5 on page 26 and Table 6 on page 27, respectively.
Default value is unprogrammed (“1”).
1
2
3
4
Memory Lock Bits
1. Program the Fuse bits before programming the Lock bits.
LB2
1
1
0
0
LB1
1
0
0
1
Protection Type
No restrictions for SPM or LPM accessing the Boot Loader
section.
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
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
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.
ATmega323(L)
187