fuse | default | meaning | page |
CKSEL3..1 | 000 | select the clock from internal RC, ceramic, XTAL, external clock | 23,24,27 |
CKSEL0 | 1 | select the clock from internal RC, ceramic, XTAL, external clock | 25,255 |
CKOPT | 1 | clock amplifier for crystal oscillator or so, depends on the clocksource itself | 24 |
SUT1..0 | 10 | startup time selector | 25,26,27,28,29,255 |
OCDEN | 1 | never ship as programmed | 254 |
SPIEN | 0 | enable SPI programming mode | 254 |
JTAGEN | 0 | enable JTAG programming | 254 |
EESave | 1 | preserve EEPROM through chip erase | 254 |
BOOTSZ1..0 | 00 | select boot sector size as 00=2k at 3800, 01=1k at 3C00, 10=512 at 3E00, 11=256 at 3F00 |
252 |
BOOTRST | 1 | select boot reset vector, 0 = in bootsector, at 0000 otherwise, set IVSEL in MCUCR register for the interrupts | 245 |
BODLEVEL | 1 | brownout detection on 2.7V = 1, or 4.0V = 0 | 35,37 |
BODEN | 1 | brownout detection enabled = 0 | 37 |
CKOPT | CKSEL3..1 | freq range MHZ | recommended caps |
1 | 101 | 0.4 - 0.9 | for resonators only |
1 | 110 | 0.9 - 3.0 | 12 - 22pF |
1 | 111 | 3.0 - 8.0 | 12 - 22pF |
0 | 101, 110, 111 | 1.0 - | 12 - 22pF |
CKSEL0 | SUT1..0 | startup time | additional reset delay | recommended usage |
0 | 00 | 258 clk | 4.1ms | ceramic, fast rising power, not frequency stable at startup |
0 | 01 | 258 clk | 65ms | ceramic, slow rising power, not frequency stable at startup |
0 | 10 | 1k clk | - | ceramic, BOD enabled, frequency stable at startup |
0 | 11 | 1k clk | 4.1ms | ceramic, fast rising power, frequency stable at startup |
1 | 00 | 1k clk | 65ms | ceramic, slow rising power, frequency stable at startup |
1 | 01 | 16k clk | - | crystal, BOD enabled |
1 | 10 | 16k clk | 4.1ms | crystal, fast rising power |
1 | 11 | 16k clk | 65ms | crystal, slow rising power |
SUT1..0 | Startup from powerdown & powersave | additionaldelayfrom reset @ Vcc=5V | recommended usage |
00 | 1k clk | 4.1ms | fast rising power or BOD enabled |
01 | 1k clk | 65ms | slowly rising power |
10 | 32k clk | 65ms | Stable frequency at startup |
11 | reserved | reserved | reserved |
CKSEL3..0 | Nominal frequency |
0101 | <= 0.9 MHz |
0110 | 0.9 - 3.0 MHz |
0111 | 3.0 - 8.0 MHz |
1000 | 8.0 - 12.0 MHz |
SUT1..0 | Startup from powerdown & powersave | additionaldelayfrom reset @ Vcc=5V | recommended usage |
00 | 18clk | - | BOD enabled |
01 | 18clk | 4.1ms | fast rising power |
10 | 18clk | 65ms | Slowly rising power |
11 | 6clk | 4.1ms | fast rising power or BOD enabled |
CKSEL3..0 | Nominal frequency |
0001 | 1.0 MHz |
0010 | 2.0 MHz |
0011 | 4.0 MHz |
0100 | 8.0 MHz |
SUT1..0 | Startup from powerdown & powersave | additionaldelayfrom reset @ Vcc=5V | recommended usage |
00 | 6clk | - | BOD enabled |
01 | 6clk | 4.1ms | fast rising power |
10 | 6clk | 65ms | Slowly rising power |
11 | reserved | reserved | reserved |
OSCCAL value | min frequency in percentage from nominal | max frequency in percentage from nominal |
$00 | 50 | 100 |
$7F | 75 | 150 |
$FF | 100 | 200 |
SUT1..0 | Startup from powerdown & powersave | additionaldelayfrom reset @ Vcc=5V | recommended usage |
00 | 6clk | - | BOD enabled |
01 | 6clk | 4.1ms | fast rising power |
10 | 6clk | 65ms | Slowly rising power |
11 | reserved | reserved | reserved |