Atmel Xplained Evaluation Board AT32UC3A3-XPLD AT32UC3A3-XPLD Data Sheet

32072H–AVR32–10/2012

If the current command writes or erases a page in a locked region, or a page protected by the
BOOTPROT fuses, the command has no effect on the flash memory; however, the LOCKE flag
is set in the FSR register. This flag is automatically cleared by a read access to the FSR register.

Flash technology requires that an erase must be done before programming. The entire flash can
be erased by an Erase All command. Alternatively, pages can be individually erased by the
Erase Page command.

The User page can be written and erased using the mechanisms described in this chapter.

After programming, the page can be locked to prevent miscellaneous write or erase sequences.
Locking is performed on a per-region basis, so locking a region locks all pages inside the region.
Additional protection is provided for the lowermost address space of the flash. This address
space is allocated for the Boot Loader, and is protected both by the lock bit(s) corresponding to
this address space, and the BOOTPROT[2:0] fuses.

Data to be written are stored in an internal buffer called page buffer. The page buffer contains w
words. The page buffer wraps around within the internal memory area address space and
appears to be repeated by the number of pages in it. Writing of 8-bit and 16-bit data to the page
buffer is not allowed and may lead to unpredictable data corruption. 

Data must be written to the page buffer before the programming command is written to the Flash
Command Register FCMD. The sequence is as follows:

• Reset the page buffer with the Clear Page Buffer command.

• Fill the page buffer with the desired contents, using only 32-bit access.

• Programming starts as soon as the programming key and the programming command are 

written to the Flash Command Register. The PAGEN field in the Flash Command Register 
(FCMD) must contain the address of the page to write. PAGEN is automatically updated 
when writing to the page buffer, but can also be written to directly. The FRDY bit in the Flash 
Status Register (FSR) is automatically cleared when the page write operation starts.

• When programming is completed, the bit FRDY in the Flash Status Register (FSR) is set. If 

an interrupt was enabled by setting the bit FRDY in FCR, the interrupt line of the flash 
controller is set.

Two errors can be detected in the FSR register after a programming sequence:

• Programming Error: A bad keyword and/or an invalid command have been written in the 

FCMD register.

• Lock Error: The page to be programmed belongs to a locked region. A command must be 

executed to unlock the corresponding region before programming can start.

The entire memory is erased if the Erase All command (EA) is written to the Flash Command
Register (FCMD). Erase All erases all bits in the flash array. The User page is not erased. All
flash memory locations, the general-purpose fuse bits, and the security bit are erased (reset to
0xFF) after an Erase All.

The EA command also ensures that all volatile memories, such as register file and RAMs, are
erased before the security bit is erased.

Erase All operation is allowed only if no regions are locked, and the BOOTPROT fuses are pro-
grammed with a region size of 0. Thus, if at least one region is locked, the bit LOCKE in FSR is