FUJITSU F2MCTM-16LX - Manual (Page 567)

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CHAPTER 24 512K-BIT FLASH MEMORY
24.9 Flash Security Feature
Flash security feature provides possibilities to protect the content of the flash memory.
■ Abstract
By writing the protection code of "01
H
" to the security bit in the flash memory, access to the flash memory
is restricted. Once the flash memory is protected, performing the chip erase operation only can unlock the
function. Otherwise, read/write access to the flash memory from the external pins is not possible.
This function is suitable for applications requiring security of self-containing and data stored in the flash
memory.
Address of the security bit depends on the size of built-in flash memory. Table 24.9-1 shows the address of
security bit.
■ How to Enable the Flash Security Feature
After writing the protection code "01
H
" to the security bit, the following external reset or power-on enables
the Flash Security Feature.
■ How to Disable the Flash Security Feature
Performing the chip erase operation.
■ Behavior Under the Flash Security Feature
Read operation: invalid data read
Write operation: ignored
■ Others
(1) About configuration of the general-purpose parallel programmer, please follow to the specification of
parallel programmer.
(2) Writing the protection code at the last of flash memory programming is recommended, in order to
prevent the device from enabling the Flash Security Feature accidentally.
Notes:
• The flash security bit is allocated in the flash memory area. When the protection code "01
H
" is written to
the security bit, it is locked by the security. So, when not using the security function, do not write "01
H
"
to this address.
See Table 24.9-1 for the address of the security bit.
• By specifying the sector of the flash memory, it cannot be locked the security per sector. It is the
security function for all areas in the flash memory.
• The FLASH memory trouble in the state to put security cannot be analyzed at all.
Table 24.9-1 Address of Flash Security Bit
Flash memory size Address of security bit
MB90F362/T(S), MB90F367/T(S) Built-in 512K-bit flash memory FF0001
H