MEGA128CAN Datasheet, PDF (315/413 Pages) ATMEL Corporation – Microcontroller WITH 128K BYTES OF ISP FLASH AND CAN CONTROLLER

AT90CAN128
See Table 115 and Table 116 for further details. The Boot Lock bits can be set in soft-
ware and in Serial or Parallel Programming mode, but they can be cleared by a Chip
Erase command only. The general Write Lock (Lock Bit mode 2) does not control the
programming of the Flash memory by SPM instruction. Similarly, the general
Read/Write Lock (Lock Bit mode 1) does not control reading nor writing by LPM/SPM
(Load Program Memory / Store Program Memory) instructions, if it is attempted.
Table 115. Boot Lock Bit0 Protection Modes (Application Section)⁽¹⁾
Lock Bit
Mode BLB02 BLB01 Protection
1
1
1
No restrictions for SPM or LPM accessing the Application
section.
2
1
0
SPM is not allowed to write to the Application section.
3
0
0
SPM is not allowed to write to the Application section, and
LPM executing from the Boot Loader section is not allowed
to read from the Application section. If Interrupt Vectors are
placed in the Boot Loader section, interrupts are disabled
while executing from the Application section.
4
0
1
LPM executing from the Boot Loader section is not allowed
to read from the Application section. If Interrupt Vectors are
placed in the Boot Loader section, interrupts are disabled
while executing from the Application section.
Note: 1. “1” means unprogrammed, “0” means programmed
Table 116. Boot Lock Bit1 Protection Modes (Boot Loader Section)⁽¹⁾
Lock Bit
Mode BLB12 BLB11 Protection
1
1
1
No restrictions for SPM or LPM accessing the Boot Loader
section.
2
1
0
SPM is not allowed to write to the Boot Loader section.
3
0
0
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.
4
0
1
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.
Note: 1. “1” means unprogrammed, “0” means programmed
Entering the Boot Loader
Program
Entering the Boot Loader takes place by a jump or call from the application program.
This may be initiated by a trigger such as a command received via USART, or SPI inter-
face. Alternatively, the Boot Reset Fuse can be programmed so that the Reset Vector is
pointing to the Boot Flash start address after a reset. In this case, the Boot Loader is
started after a reset. After the application code is loaded, the program can start execut-
ing the application code. Note that the fuses cannot be changed by the MCU itself. This
means that once the Boot Reset Fuse is programmed, the Reset Vector will always
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