ST7LITE1XB datasheet(14/157 Pages) STMICROELECTRONICS

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ST7LITE1xB

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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 Related Documentation

For details on Flash programming and ICC proto-

col, refer to the ST7 Flash Programming Refer-

ence Manual and to the ST7 ICC Protocol Refer-

ence Manual

4.7 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.

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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