MEGA128CAN Datasheet, PDF (327/413 Pages) ATMEL Corporation – Microcontroller WITH 128K BYTES OF ISP FLASH AND CAN CONTROLLER

Latching of Fuses
4250E–CAN–12/04
AT90CAN128
Table 125. Fuse High Byte (Continued)
Fuse High Bit
Byte
No Description
Default Value
BOOTSZ1
2
Select Boot Size
(see Table 119 for details)
0 (programmed)⁽²⁾
BOOTSZ0
1
Select Boot Size
(see Table 119 for details)
0 (programmed)⁽²⁾
BOOTRST 0 Select Reset Vector
1 (unprogrammed)
Note: 1. The SPIEN Fuse is not accessible in serial programming mode.
2. The default value of BOOTSZ1..0 results in maximum Boot Size. See Table 119 on
page 323 for details.
3. See “Watchdog Timer Control Register – WDTCR” on page 54 for details.
4. Never ship a product with the OCDEN Fuse programmed regardless of the setting of
Lock bits and JTAGEN Fuse. A programmed OCDEN Fuse enables some parts of
the clock system to be running in all sleep modes. This may increase the power
consumption.
5. If the JTAG interface is left unconnected, the JTAGEN fuse should if possible be dis-
abled. This to avoid static current at the TDO pin in the JTAG interface.
Table 126. Fuse Low Byte
Fuse Low
Byte
CKDIV8⁽⁴⁾
CKOUT⁽³⁾
Bit
No Description
7 Divide clock by 8
6 Clock output
Default Value
0 (programmed)
1 (unprogrammed)
SUT1
SUT0
CKSEL3
CKSEL2
CKSEL1
CKSEL0
5 Select start-up time
4 Select start-up time
3 Select Clock source
2 Select Clock source
1 Select Clock source
0 Select Clock source
1 (unprogrammed)⁽¹⁾
0 (programmed)⁽¹⁾
0 (programmed)⁽²⁾
0 (programmed)⁽²⁾
1 (unprogrammed)⁽²⁾
0 (programmed)⁽²⁾
Note:
1. The default value of SUT1..0 results in maximum start-up time for the default clock
source. See Table 12 on page 39 for details.
2. The default setting of CKSEL3..0 results in internal RC Oscillator @ 8 MHz. See
Table 5 on page 35 for details.
3. The CKOUT Fuse allow the system clock to be output on Port PC7. See “Clock Out-
put Buffer” on page 40 for details.
4. See “System Clock Prescaler” on page 41 for details.
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.
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.
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