Datasheet

263
32117D–AVR-01/12
AT32UC3C
through a dedicated Peripheral Bus address. Some of the general-purpose fuse bits are
reserved for special purposes, and should not be used for other functions.:
Table 15-2. General-purpose Fuses with Special Functions
General-
purpose fuse
number Name Usage
15:0 LOCK Region lock bits.
16 EPFL
External Privileged Fetch Lock. Used to prevent the CPU from
fetching instructions from external memories when in privileged
mode. This bit can only be changed when the security bit is
cleared. The address range corresponding to external
memories is device-specific, and not known to the Flash
Controller. This fuse bit is simply routed out of the CPU or bus
system, the Flash Controller does not treat this fuse in any
special way, except that it can not be altered when the security
bit is set.
If the security bit is set, only an external JTAG Chip Erase can
clear EPFL. No internal commands can alter EPFL if the
security bit is set.
When the fuse is erased (i.e. "1"), the CPU can execute
instructions fetched from external memories. When the fuse is
programmed (i.e. "0"), instructions can not be executed from
external memories.
This fuse has no effect in devices with no External Memory
Interface (EBI).
19:17 BOOTPROT
Used to select one of eight different bootloader sizes. Pages
included in the bootloader area can not be erased or
programmed except by a JTAG chip erase. BOOTPROT can
only be changed when the security bit is cleared.
If the security bit is set, only an external JTAG Chip Erase can
clear BOOTPROT, and thereby allow the pages protected by
BOOTPROT to be programmed. No internal commands can
alter BOOTPROT or the pages protected by BOOTPROT if the
security bit is set.
21:20 SECURE
Used to configure secure state and secure state debug
capabilities. Refer to the AVR32 Architecture Manual and the
AVR32UC Technical Reference Manual for more details.
22 UPROT
If programmed (i.e. “1”), the JTAG USER PROTECTION
feature is enabled. If this fuse is programmed some HSB
addresses will be accessible by JTAG access even if the flash
security fuse is programmed. Refer to the JTAG documentation
for more information on this functionality. This bit can only be
changed when the security bit is cleared.