RM0444 Rev 5 71/1390
RM0444 Embedded Flash memory (FLASH)
118
3.3.2 FLASH empty check
During the OBL phase, after loading all options, the Flash memory interface checks whether
the first location of the Main memory is programmed. The result of this check in conjunction
with the boot0 and boot1 information is used to determine where the system has to boot
from. It prevents the system to boot from Main Flash memory area when i.e. no user code
has been programmed.
The Main Flash memory empty check status can be read from the EMPTY bit in FLASH
access control register (FLASH_ACR). Software can modify the Main Flash memory empty
status by writing an appropriate value to the EMPTY bit.
3.3.3 FLASH error code correction (ECC)
Data in Flash memory words are 72-bits wide: eight bits are added per each double word
(64 bits). The ECC mechanism supports:
• One error detection and correction
• Two errors detection
When one error is detected and corrected, the flag ECCC (ECC correction) is set in FLASH
ECC register (FLASH_ECCR). If ECCCIE is set, an interrupt is generated.
When two errors are detected, a flag ECCD (ECC detection) is set in FLASH ECC register
(FLASH_ECCR). In this case, a NMI is generated.
When an ECC error is detected, the address of the failing double word is saved in
ADDR_ECC[16:0] bitfield of the FLASH_ECCR register. ADDR_ECC[2:0] are always
cleared. The bus-ID of the CPU accessing the address is saved in CPUID[2:0].
While ECCC or ECCD is set, FLASH_ECCR is not updated if a new ECC error occurs.
FLASH_ECCR is updated only when ECC flags are cleared.
Table 11. Flash memory organization for 512 Kbytes dual-bank devices
Area Addresses Size (bytes)
Memory
type
Information
block
Bank 1 0x1FFF 7800 - 0x1FFF 787F 128 Option bytes
Bank 1 0x1FFF 7000 - 0x1FFF 73FF 1 K OTP area
Bank 1 0x1FFF 0000 - 0x1FFF 6FFF 28 K System memory
Main
memory
Bank 2
0x0807 F804 - 0x0807 FFFF 2 K Page 383
... ... ...
0x0804 1000 - 0x0804 17FF 2 K Page 258
0x0804 0800 - 0x0804 0FFF 2 K Page 257
0x0804 0000 - 0x0804 07FF 2 K Page 256
Bank 1
0x0803 F800 - 0x0803 FFFF 2 K Page 127
... ... ...
0x0800 1000 - 0x0800 17FF 2 K Page 2
0x0800 0800 - 0x0800 0FFF 2 K Page 1
0x0800 0000 - 0x0800 07FF 2 K Page 0
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