Datasheet

145
32142D–06/2013
ATUC64/128/256L3/4U
The SECURE fuses have the following functionality:
To erase or write a general-purpose fuse bit, the commands Write General-Purpose Fuse Bit
(WGPB) and Erase General-Purpose Fuse Bit (EGPB) are provided. Writing one of these com-
mands, together with the number of the fuse to write/erase, performs the desired operation.
An entire General-Purpose Fuse byte can be written at a time by using the Program GP Fuse
Byte (PGPFB) instruction. A PGPFB to GP fuse byte 2 is not allowed if the flash is locked by the
security bit. The PFB command is issued with a parameter in the PAGEN field:
• PAGEN[2:0] - byte to write
• PAGEN[10:3] - Fuse value to write
All general-purpose fuses can be erased by the Erase All General-Purpose fuses (EAGP) com-
mand. An EAGP command is not allowed if the flash is locked by the security bit.
Two errors can be detected in the FSR register after issuing these commands:
• Programming Error: A bad keyword and/or an invalid command have been written in the
FCMD register.
• Lock Error:
– A write or erase of the BOOTPROT or EPFL or UPROT fuse bits was attempted
while the flash is locked by the security bit.
– A write or erase of the SECURE fuse bits was attempted when SECURE mode was
enabled.
The lock bits are implemented using the lowest 16 general-purpose fuse bits. This means that
the 16 lowest general-purpose fuse bits can also be written/erased using the commands for
locking/unlocking regions, see Section 9.5.3.
Table 9-3. Boot Loader Area Specified by BOOTPROT
BOOTPROT
Pages protected by
BOOTPROT
Size of protected
memory
7None 0
60-1 1Kbyte
50-3 2Kbyte
40-7 4Kbyte
3 0-15 8Kbyte
20-31 16Kbyte
10-63 32Kbyte
0 0-127 64Kbyte
Table 9-5. Secure State Configuration
SECURE Functionality SSE SSDE
00 Secure state disabled 0 0
01 Secure enabled, secure state debug enabled 1 1
10 Secure enabled, secure state debug disabled 1 0
11 Secure state disabled 0 0