Analysis of AVR fuse settings

AVR chips use fuses to set the clock, boot time, enable some functions, BOOT area settings, and of course the most troublesome confidentiality bit for beginners. If you don't set it well, it will be very troublesome to lock the chip. To minimize the power consumption of the MCU, you also need to understand the settings of some bits. 1: Unprogrammed 0: Programmed 1. BOD (Brown-out Detection) brown-out detection circuit BODLEVEL (BOD level selection): 1: 2.7V level; 0: 4.0V level BODEN (BOD function control): 1: BOD function disabled; 0: BOD function allowed How to use: If BODEN is enabled (checkbox is selected) to start brown-out detection, the detection level is determined by BODLEVEL. Once VCC drops below the trigger level (2.7v or 4.0v), the MCU is reset; when the VCC level is greater than the trigger level, it will resume work after tTOUT delay weeks. Because M16L can work at 2.7v~5.5v, the trigger level can be selected as 2.7v (BODLEVEL=1) or 4.0v (BODLEVEL=0); while M16 works at 4.5~5.5V, so only BODLEVEL=0 can be selected. BODLEVEL=1 is not applicable to ATmega16. 2. Reset start time selection SUT 1/0: When different crystal oscillators are selected, SUT is different. If there is no special requirement, it is recommended to set the reset start time of SUT 1/0 to be slightly longer so that the power supply rises slowly. 3.CKSEL3/0: Clock source selection (clock summary table) Clock summary table Clock source start delay fuse External clock 6 CK + 0 ms CKSEL = 0000 SUT = "00" External clock 6 CK + 4.1 ms CKSEL = 0000 SUT = "01" External clock 6 CK + 65 ms CKSEL = "0000" SUT = "10" Internal RC oscillation 1MHZ 6 CK + 0 ms CKSEL = "0001" SUT = "00" Internal RC oscillation 1MHZ 6 CK + 4.1 ms CKSEL = "0001" SUT = "01" Internal RC oscillation 1MHZ1 6 CK + 65 ms CKSEL = "0001" SUT = "10" Internal RC oscillation 2MHZ 6 CK + 0 ms CKSEL = "0010" SUT = "00" Internal RC oscillation 2MHZ 6 CK + 4.1 ms CKSEL="0010" SUT="01" Internal RC oscillator 2MHZ 6 CK + 65 ms CKSEL="0010" SUT="10" Internal RC oscillator 4MHZ 6 CK + 0 ms CKSEL="0011" SUT="00" Internal RC oscillator 4MHZ 6 CK + 4.1 ms CKSEL="0011" SUT="01" Internal RC oscillator 4MHZ 6 CK + 65 ms CKSEL="0011" SUT="10" Internal RC oscillator 8MHZ 6 CK + 0 ms CKSEL="0100" SUT="00" Internal RC oscillator 8MHZ 6 CK + 4.1 ms CKSEL="0100" SUT="01" Internal RC oscillator 8MHZ 6 CK + 65 ms CKSEL="0100" SUT="10" External RC oscillation ≤ 0.9MHZ 18 CK + 0 ms CKSEL="0101" SUT="00" External RC oscillation ≤ 0.9MHZ 18 CK + 4.1 ms CKSEL="0101" SUT="01" External RC oscillation ≤ 0.9MHZ 18 CK + 65 ms CKSEL=" 0101" SUT="10" External RC oscillation ≤ 0.9MHZ 6 CK + 4.1 ms CKSEL="0101" SUT="11" External RC oscillation 0.9-3.0MHZ 18 CK + 0 ms CKSEL="0110" SUT="00" External RC oscillation 0.9-3.0MHZ 18 CK + 4.1 ms CKSEL="0110" SUT="01" External RC oscillation 0.9-3.0MHZ 18 CK + 65 ms CKSEL="0110" SUT="10" External RC oscillator 0.9-3.0MHZ 6 CK + 4.1 ms CKSEL=0110 SUT="11" External RC oscillator 3.0-8.0MHZ 18 CK + 0 ms CKSEL=0111 SUT="00" External RC oscillator 3.0-8.0MHZ 18 CK + 4.1 ms CKSEL="0111" SUT="01" External RC oscillator 3.0-8. 0MHZ 18 CK + 65 ms CKSEL = 0111 SUT = "10" External RC oscillator 3.0-8.0MHZ 6 CK + 4.1 ms CKSEL = "0111" SUT = "11" External RC oscillator 8.0-12.0MHZ 18 CK + 0 ms CKSEL = 1000 SUT = "00" External RC oscillator 8.0-12.0MHZ 18 CK + 4.1 ms CKSEL = "1000" SUT = "01" External RC oscillator 8.0-12.0MHZ 18 CK + 65 ms CKSEL = "1000" SUT = "10" External RC oscillator 8.0-12.0MHZ 6 CK + 4.1 ms CKSEL = "1000" SUT = "11"






























































































































Low frequency crystal oscillator


(32.768KHZ) 1K CK + 4.1 ms CKSEL="1001" SUT="00"Low frequency crystal oscillator (32.768KHZ) 1K CK + 65 ms CKSEL="1001" SUT="01"


Low frequency crystal oscillator (32.768KHZ) 32K CK + 65 ms CKSEL="1001" SUT="10" Low


frequency quartz/ceramic oscillator (0.4-0.9MHZ) 258 CK + 4.1 ms CKSEL="1010" SUT="00"


Low frequency quartz/ceramic oscillator (0.4-0.9MHZ) 258 CK + 65 ms CKSEL="1010" SUT="01"


Low frequency quartz/ceramic oscillator (0.4-0.9MHZ) 1K CK + 0 ms CKSEL=1010 SUT="10" Low


frequency quartz/ceramic oscillator (0.4-0.9MHZ) 1K CK + 4.1 ms CKSEL="1010" SUT="11"


Low frequency quartz/ceramic oscillator (0.4-0.9MHZ) 1K CK + 65 ms CKSEL="1011" SUT="00"


Low frequency quartz/ceramic oscillator (0.4-0.9MHZ) 16K CK + 0 ms CKSEL=1011 SUT="01"


Low frequency quartz/ceramic oscillator (0.4-0.9MHZ) 16K CK + 4.1ms CKSEL="1011" SUT="10"


Low frequency quartz/ceramic oscillator (0.4-0.9MHZ) 16K CK + 65ms CKSEL="1011" SUT="11"


Intermediate frequency quartz/ceramic oscillator (0.9-3.0MHZ) 258 CK + 4.1 ms CKSEL="1100" SUT="00"


Intermediate frequency quartz/ceramic oscillator (0.9-3.0MHZ) 258 CK + 65 ms CKSEL="1100" SUT="01"


Intermediate frequency quartz/ceramic oscillator (0.9-3.0MHZ) 1K CK + 0 ms CKSEL=1100 SUT="10"


Intermediate frequency quartz/ceramic oscillator (0.9-3.0MHZ) 1K CK + 4.1 ms CKSEL="1100" SUT="11"


Intermediate frequency quartz/ceramic oscillator (0.9-3.0MHZ) 1K CK + 65 ms CKSEL="1101" SUT="00" Intermediate


frequency quartz/ceramic oscillator (0.9-3.0MHZ) 16K CK + 0 ms CKSEL="1101" SUT="01"


Intermediate frequency quartz/ceramic oscillator (0.9-3.0MHZ) 16K CK + 4.1ms CKSEL="1101" SUT="10"


Intermediate frequency quartz/ceramic oscillator (0.9-3.0MHZ) 16K CK + 65ms CKSEL="1101" SUT="11"


High frequency quartz/ceramic oscillator (3.0-8.0MHZ) 258 CK + 4.1 ms CKSEL="111"0 SUT="00"


High frequency quartz/ceramic oscillator (3.0-8.0MHZ) 258 CK + 65 ms CKSEL="111"0 SUT ="01" High


frequency quartz/ceramic oscillator (3.0-8.0MHZ) 1K CK + 0 ms CKSEL="111"0 SUT="10" High


frequency quartz/ceramic oscillator (3.0-8.0MHZ) 1K CK + 4.1 ms CKSEL="111"0 SUT="11"


High frequency quartz/ceramic oscillator (3.0-8.0MHZ) 1K CK + 65 ms CKSEL="1111" SUT="00"


High frequency quartz/ceramic oscillator (3.0-8.0MHZ) 16K CK + 0 ms CKSEL="1111" SUT="01"


High frequency quartz/ceramic oscillator (3.0-8.0MHZ) 16K CK + 4.1ms CKSEL="111"1 SUT="10"


High frequency quartz/ceramic oscillator (3.0-8.0MHZ) 16K CK + 65ms CKSEL="1111" SUT="11"
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High bit (BOOT area setting):

1. JTAGEN (JTAG enable): 1: JTAG disabled; 0: JTAG enabled

OCDEN (OCD function enabled): 1: OCD function disabled; 0: OCD function enabled

Note: OCDEN (On-chip Debug): On-chip debug enable bit

JTAGEN (JTAG enable): JTAG test access port

How to use: During JTAG debugging, enable OCDEN JTAGEN (check the box) and keep all lock bits in unlocked state; in actual use, to reduce power consumption, do not enable OCDEN JTAGEN, which reduces the current by about 2-3mA.

2. SPIEN (SPI download enabled): 1: SPI download disabled; 0: SPI download enabled

Note: In the ISP software, SPIEN cannot be edited and is 0 by default.

3. CKOPT (Select Amplifier Mode): CKOPT = 0: High amplitude oscillation output; CKOPT

= 1: Low amplitude oscillation output

When CKOPT is programmed, the oscillator generates full amplitude oscillation at the output pin. This mode is suitable for noisy environments and when a second clock buffer needs to be driven through XTAL2, and the frequency range of this mode is relatively wide. When CKOPT is kept unprogrammed, the output signal amplitude of the oscillator is relatively small. The advantage is that the power consumption is greatly reduced, but the frequency range is relatively narrow and other clock buffers cannot be driven.

For the resonator, the maximum frequency is 8 MHz when CKOPT is not programmed and 16 MHz when CKOPT is programmed. CKOPT is not programmed when the internal RC oscillator is working.

4.EEAVE (EEPROM data retention during burning): 1: not retained; 0: retained

5.BOOTRST (reset entry selection): 1: program starts from address 0x0000 0: after reset

execute from BOOT area (refer to BOOTSZ0/1)

6.BOOTSZ 1/0 (boot area program size and entry):

00: 1024Word/0xc00;

01: 512Word/0xe00;

10: 256Word/0xf00;

11: 128Word/0xf80