ST72340 datasheet(17/191 Pages) STMICROELECTRONICS

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ST72340, ST72344, ST72345

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FLASH PROGRAM MEMORY (Cont’d)

4.5 Memory Protection

There are two different types of memory protec-

tion: Read Out Protection and Write/Erase Protec-

tion which can be applied individually.

4.5.1 Read out Protection

Readout protection, when selected provides a pro-

tection against program memory content extrac-

tion and against write access to Flash memory.

Even if no protection can be considered as totally

unbreakable, the feature provides a very high level

of protection for a general purpose microcontroller.

Both program and data E2 memory are protected.

In flash devices, this protection is removed by re-

programming the option. In this case, both pro-

gram and data E2 memory are automatically

erased, and the device can be reprogrammed.

Read-out protection selection depends on the de-

vice type:

– In Flash devices it is enabled and removed

through the FMP_R bit in the option byte.

– In ROM devices it is enabled by mask option

specified in the Option List.

4.5.2 Flash Write/Erase Protection

Write/erase protection, when set, makes it impos-

sible to both overwrite and erase program memo-

ry. It does not apply to E2 data. Its purpose is to

provide advanced security to applications and pre-

vent any change being made to the memory con-

tent.

Warning: Once set, Write/erase protection can

never be removed. A write-protected flash device

is no longer reprogrammable.

Write/erase protection is enabled through the

FMP_W bit in the option byte.

4.6 Register Description

FLASH CONTROL/STATUS REGISTER (FCSR)

Read/Write

Reset Value: 000 0000 (00h)

1st RASS Key: 0101 0110 (56h)

2nd RASS Key: 1010 1110 (AEh)

Note: This register is reserved for programming

using ICP, IAP or other programming methods. It

controls the XFlash programming and erasing op-

erations. For details on XFlash programming, refer

to the ST7 Flash Programming Reference Manual.

When an EPB or another programming tool is

used (in socket or ICP mode), the RASS keys are

sent automatically.

000

OPT

LAT

PGM

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