NXP Semiconductors
UM11227
NTM88 family of tire pressure monitor sensors
UM11227 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2020. All rights reserved.
User manual Rev. 6 — 24 April 2020
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• Writing to a FLASH address while FCBEF is not set (A new command cannot be
started until the command buffer is empty.)
• Writing a second time to a FLASH address before launching the previous command
(There is only one write to FLASH for every command.)
• Writing a second time to FCMD before launching the previous command (There is only
one write to FCMD for every command.)
• Writing to any FLASH control register other than FCMD after writing to a FLASH
address
• Writing any command code other than the five allowed codes ($05, $20, $25, $40, or
$41) to FCMD
• Accessing (read or write) any FLASH control register other than the write to FSTAT (to
clear FCBEF and launch the command) after writing the command to FCMD.
• The MCU enters STOP mode while a program or erase command is in progress (The
command is aborted.)
• Writing the byte program, burst program, or page erase command code ($20,
$25, or $40) with a BACKGROUNDDEBUG command while the MCU is secured
(the BACKGROUND DEBUG controller can only do blank check and mass erase
commands when the MCU is secure.)
• Writing 0 to FCBEF to cancel a partial command.
10.24.6 FMC block protection
The block protection feature prevents the protected region of FLASH from program or
erase changes. Block protection is controlled through the FLASH Protection Register
(FPROT). When enabled, block protection begins at any 512-byte boundary below the
last address of FLASH, $FFFF.
After exit from reset, FPROT is loaded with the contents of the NVPROT location
which is in the nonvolatile register block of the FLASH memory. FPROT cannot be
changed directly from application software so a runaway program cannot alter the
block protection settings. Because NVPROT is within the last 512 bytes of FLASH, if
any amount of memory is protected, NVPROT is itself protected and cannot be altered
(intentionally or unintentionally) by the application software. FPROT can be written
through BACKGROUND DEBUG commands which allows a way to erase and reprogram
a protected FLASH memory.
The block protection mechanism is illustrated below. The FPS bits are used as the upper
bits of the last address of unprotected memory. This address is formed by concatenating
FPS7:FPS1 with logic 1 bits as shown. For example, in order to protect the last 8192
bytes of memory (addresses $E000 through $FFFF), the FPS bits must be set to 1101
111 which results in the value $DFFF as the last address of unprotected memory. In
addition to programming the FPS bits to the appropriate value, FPDIS (bit 0 of NVPROT)
must be programmed to logic 0 to enable block protection. Therefore the value $DE must
be programmed into NVPROT to protect addresses $E000 through $FFFF.
One use for block protection is to block protect an area of FLASH memory for a boot
loader program. This boot loader program then can be used to erase the rest of the
FLASH memory and reprogram it. Because the boot loader is protected, it remains intact
even if MCU power is lost in the middle of an erase and reprogram operation.
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