SAM4L Datasheet, PDF (269/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
14.6.1
Write/Erase Page Operation
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.
Data to be written is stored in an internal buffer called the 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:
• Erase the page to be programmed.
• Reset the page buffer with the Clear Page Buffer command.
• Fill the page buffer with the desired contents as described in Section 14.5.8 on page 264.
• 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 FRDY bit in the Flash Status Register (FSR) is set. If
an interrupt was enabled by writing FCR.FRDY to one, an interrupt request is generated.
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: Can have two different causes:
– The page to be programmed belongs to a locked region. A command must be
executed to unlock the corresponding region before programming can start.
– A bus master without secure status attempted to program a page requiring secure
privileges.
14.6.2
Erase All Operation
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 fuses 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 fuses are erased.
Erase All operation is allowed only if no regions are locked. Thus, if at least one region is locked,
the bit LOCKE in FSR is set and the command is cancelled. If the LOCKE bit in FCR is one, an
interrupt request is set generated.
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