ST10F269Z1Q6 datasheet(24/184 Pages) STMICROELECTRONICS

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5 - INTERNAL FLASH MEMORY

ST10F269

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Protection Status will return the new PR

value only after a reset.

Block Temporary Unprotection (BTU). This Instruction can be used to temporary unprotect all the

blocks from Program / Erase protection. The Unprotection is disabled after a Reset cycle. The Block

Temporary Unprotection command xxC1h must be given to enable Block Temporary Unprotection. The

Command must be preceded by the CI-Protection Enable cycles and followed by the Read/Reset

command xxF0h.

Set Code Protection (SCP). This kind of protection allows the customer to protect the proprietary code

written in Flash. If installed and active, Flash Code Protection prevents data operand accesses and

program branches into the on-chip Flash area from any location outside the Flash memory itself. Data

operand accesses and branches to Flash locations are only and exclusively allowed for instructions

executed from the Flash memory itself. Every read or jump to Flash performed from another memory (like

internal RAM, external memory) while Code Protection is enabled, will give the opcode 009Bh related to

TRAP #00 illegal instruction. The CI-Protection Enable cycles must be sent to set the Code Protection. By

writing data 7FFFh at any odd word address, the Code Protected status is stored in the Flash Protection

disable the Code Protection using Code Temporary Unprotection instruction.

Note: Bits that are already at ’0’ in protection register must be confirmed at ’0’ also in data latched during

the 4th cycle of set protection command, otherwise an error may occur.

Code Temporary Unprotection (CTU). This instruction must be used to temporary disable Code

Protection. This instruction is effective only if executed from Flash memory space. To restore the

protection status, without using a reset, it is necessary to use a Code Temporary Protection instruction.

System reset will reset also the Code Temporary Unprotected status. The Code Temporary Unprotection

command consists of the following write cycle:

MOV

MEM, Rn

; This instruction MUST be executed from Flash memory space

Where MEM is an absolute address inside memory space, Rn is a register loaded with data 0FFFFh.

Code Temporary Protection (CTP). This instruction allows to restore Code Protection. This operation is

effective only if executed from Flash memory and is necessary to restore the protection status after the

use of a Code Temporary Unprotection instruction.

The Code Temporary Protection command consists of the following write cycle:

MOV

MEM, Rn

; This instruction MUST be executed from Flash memory space

Where MEM is an absolute address inside memory space, Rn is a register loaded with data 0FFFBh.

Note that Code Temporary Unprotection instruction must be used when it is necessary to modify the

Flash with protected code (SCP), since the write/erase routines must be executed from a memory

external to Flash space. Usually, the write/erase routines, executed in RAM, ends with a return to Flash

space where a CTP instruction restore the protection.

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