st10f269z1 STMicroelectronics, st10f269z1 Datasheet - Page 24

• Manufacturer Part Number: st10f269z1
• Description: St10f269 16-bit Mcu With Mac Unit, 256k Byte Flash Memory And 12k Byte Ram
• Manufacturer: STMicroelectronics

5 - INTERNAL FLASH MEMORY
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
Register (PR). Protection is permanent and cannot be cleared by the user. It is possible to temporarily
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
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
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
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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Protection Status will return the new PR
value only after a reset.
the 4th cycle of set protection command, otherwise an error may occur.
MEM, Rn
MEM, Rn
; This instruction MUST be executed from Flash memory space
; This instruction MUST be executed from Flash memory space
ST10F269