ST92124V1Q-Auto STMicroelectronics, ST92124V1Q-Auto Datasheet - Page 63

• Manufacturer Part Number: ST92124V1Q-Auto
• Description: 8-bit MCU for automotive
• Manufacturer: STMicroelectronics

Specifications of ST92124V1Q-Auto

• Internal Memory: Single Voltage FLASH up to 256 Kbytes, RAM up to 8Kbytes, 1K byte E3 TM (Emulated EEPROM)
• Minimum Instruction Time: 83 ns (24 MHz int. clock)

PROTECTION STRATEGY (Cont’d)
NON VOLATILE PASSWORD (NVPWD1-0)
Address: 231FFF-231FFEh - Write Only
Delivery value: 1111 1111 (FFh)
Bit 7:0 = PWD[7:0]: Password bits 7:0 (Write On-
ly).
These bits must be programmed with the Non Vol-
atile Password that must be provided with the Set
Protection operation to disable (first write access)
or to reenable (second write access) the test and
EPB modes. The first write access fixes the pass-
word value and resets the TMDIS bit of NVWPR
(231FFDh). The second write access, with Pro-
gram Data matching with NVPWD[1:0] content, re-
sets the PWOK bit of NVWPR.
These two registers can be accessed only in write
mode (a read access returns FFh).
3.5.2 Temporary Unprotection
On user request the memory can be configured so
as to allow the temporary unprotection also of all
access protections bits of NVAPR (write protection
bits of NVWPR are always temporarily unprotecta-
ble).
PWD7 PWD6 PWD5 PWD4 PWD3 PWD2 PWD1 PWD0
7
6
5
4
3
2
1
0
ST92124xxx-Auto/150xxxxx-Auto/250xxxx-Auto
Bit APEX can be temporarily disabled by execut-
ing the Set Protection operation and writing 1 into
this bit, but only if this write instruction is executed
from an internal memory (Flash and Test Flash ex-
cluded).
Bit APEE can be temporarily disabled by execut-
ing the Set Protection operation and writing 1 into
this bit, but only if this write instruction is executed
from the memory itself to unprotect (
Bits APRO and APBR can be temporarily disabled
through a direct write at NVAPR location, by over-
writing at 1 these bits, but only if this write instruc-
tion is executed from the memory itself to unpro-
tect.
To restore the access protections, reset the micro
or execute another Set Protection operation by
writing 0 to the desired bits.
Note: To restore all the protections previously en-
abled in the NVAPR or NVWPR register, read the
corresponding register.
When an internal memory (Flash, TestFlash or
E
through a DMA of a peripheral is forbidden (it re-
turns FFh). To read data in DMA mode from a pro-
tected memory, first it is necessary to temporarily
unprotect that memory.
The temporary unprotection allows also to update
a protected code.
Refer to the following figures to manage the Test/
EPB, Access and Write protection modes.
3 TM
) is protected in access, also the data access
E
3 TM
).
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