ST7L09 datasheet(14/104 Pages) STMICROELECTRONICS

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FLASH PROGRAM MEMORY (Cont’d)

4.5 MEMORY PROTECTION

Two different types of memory protection exist:

Read-out Protection and Write/Erase Protection,

which are applied individually.

4.5.1 Read-out Protection

Read-out protection, when selected provides a

protection against program memory content ex-

traction and against write access to Flash memo-

ry. Even if no protection is 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 is 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

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.

Table 4. Flash Register Map and Reset Values

OPT

LAT

PGM

Address

(Hex.)

Label

765

43210

002Fh

FCSR

Reset Value

000

OPT

LAT

PGM

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