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CHAPTER 17 FLASH MEMORY
17.6 Flash Security Feature
Flash security feature provides possibilities to protect the content of the flash memory
from being read from external.
■ Abstract
By writing the protection code of "01
H
" to the predefined flash security address of the flash memory,
access to the flash memory is restricted. Once the flash memory is protected, unlock the security function
can only be done by performing the chip erase operation. Otherwise, read/write access of the flash memory
from the external pins is not possible. This function is suitable for applications requiring security of self-
containing data stored in the flash memory.
Table 17.6-1 Flash Security Address
■
How to enable the Flash Security Feature
After writing the code "01
H
" to the flash security address, the subsequent external reset or power on
enables the flash security feature.
■
How to disable the Flash Security Feature
Perform the chip erase operation.
■
Behavior under the Flash Security Feature
Read operation: invalid data read
Write operation: ignored
■
Others
• For the configuration of the standard parallel programmer, please follow the specification of parallel
programmer.
• In order to prevent the device form enabling the flash security feature accidentally, writing the
protection code at the last of flash memory programming is recommended.
Note:
The security byte is allocated inside the flash memory. After writing the code "01
H
" to the flash security
address, the subsequent external reset or power on enables the flash security feature. Therefore, if the
flash security feature is not required, do not write "01
H
" to the security byte address.
Once the flash security feature is enabled, all the flash memory failure analysis cannot be performed.
Product Flash Memory Size Flash Security Address
MB89F202/F202RA 16 Kbyte FFFC
H