258
Atmel ATmega16/32/64/M1/C1 [DATASHEET]
7647K–AVR–12/13
Notes: 1.
The default value of SUT1..0 results in maximum start-up time for the default clock source. See
Table 5-9 on page2.
The default setting of CKSEL3..0 results in internal RC oscillator at 8MHz. See
Table 5-9 on page 32 for details.
3.
4.
The status of the fuse bits is not affected by chip erase. Note that the Fuse bits are locked if Lock bit1 (LB1) is programmed.
Program the fuse bits before programming the lock bits.
25.3.1 Latching of Fuses
The fuse values are latched when the device enters programming mode and changes of the fuse values will have no effect until
the part leaves programming mode. This does not apply to the EESAVE fuse which will take effect once it is programmed. The
fuses are also latched on power-up in normal mode.
25.4
Signature Bytes
All Atmel microcontrollers have a three-byte signature code which identifies the device. This code can be read in both serial
and parallel mode, also when the device is locked. The three bytes reside in a separate address space.
25.4.1 Signature Bytes
For the ATmega16M1 the signature bytes are:
1.
0x000: 0x1E (indicates manufactured by Atmel).
2.
0x001: 0x94 (indicates 16kB flash memory).
3.
0x002: 0x84 (indicates ATmega16M1 device when 0x001 is 0x94).
For the ATmega32M1 the signature bytes are:
1.
0x000: 0x1E (indicates manufactured by Atmel).
2.
0x001: 0x95 (indicates 32kB flash memory).
3.
0x002: 0x84 (indicates ATmega32M1 device when 0x001 is 0x95).
For the ATmega64M1 the signature bytes are:
1.
0x000: 0x1E (indicates manufactured by Atmel).
2.
0x001: 0x96 (indicates 64kB flash memory).
3.
0x002: 0x84 (indicates ATmega64M1 device when 0x001 is 0x96).
For the ATmega32C1 the signature bytes are:
1.
0x000: 0x1E (indicates manufactured by Atmel).
2.
0x001: 0x95 (indicates 32kB flash memory).
3.
0x002: 0x86 (indicates ATmega32C1 device when 0x001 is 0x95).
Table 25-7. Fuse Low Byte
Low Fuse Byte
Bit No
Description
Default Value
7
Divide clock by 8
0 (programmed)
6
Clock output
1 (unprogrammed)
SUT1
5
Select start-up time
SUT0
4
Select start-up time
CKSEL3
3
Select Clock source
CKSEL2
2
Select Clock source
CKSEL1
1
Select Clock source
CKSEL0
0
Select Clock source