SAM4L Datasheet, PDF (270/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
When the command is complete, the FRDY bit in the Flash Status Register (FSR) is set. If an
interrupt has been enabled by writing FCR.FRDY to one, an interrupt request is generated. Two
errors can be detected in the FSR register after issuing the command:
• Programming Error: A bad keyword and/or an invalid command have been written in the
FCMD register.
• Lock Error: At least one lock region is protected. The erase command has been aborted and
no page has been erased. A “Unlock region containing given page” (UP) command must be
executed to unlock any locked regions.
14.6.3
Region Lock Bits
The flash memory has p pages, and these pages are grouped into 16 lock regions, each region
containing p/16 pages. Each region has a dedicated lock bit preventing writing and erasing
pages in the region. After production, the device may have some regions locked. These locked
regions are reserved for a boot or default application. Locked regions can be unlocked to be
erased and then programmed with another application or other data.
To lock or unlock a region, the commands Lock Region Containing Page (LP) and Unlock
Region Containing Page (UP) are provided. Writing one of these commands, together with the
number of the page whose region should be locked/unlocked, performs the desired operation.
One error can be detected in the FSR register after issuing the command:
• Programming Error: A bad keyword and/or an invalid command have been written in the
FCMD register.
The lock bits are implemented using the lowest 16 general-purpose fuse bits. This means that
lock bits can also be set/cleared using the commands for writing/erasing general-purpose fuse
bits, see Section 14.7. The general-purpose bit being in an erased (1) state means that the
region is unlocked.
14.7
General-purpose Fuse Bits
The flash memory has a number of general-purpose fuse bits that the application programmer
can use freely. The fuse bits can be written and erased using dedicated commands, and read
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 14-2. General-purpose Fuses with Special Functions
General-
Purpose fuse
number
Name
Usage
15:0
LOCK
Region lock bits.
42023C–SAM–02/2013
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 fuses. The PFB command is issued with a parameter in the PAGEN field:
• PAGEN[2:0] - byte to write
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