NXP Semiconductors MC9S08LG16, Reference Manual

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Chapter 4 Memory
MC9S08LG32 MCU Series, Rev. 5
Freescale Semiconductor 59
4.4.1 Reserved Flash Locations
Several reserved flash memory locations, shown in Table 4-5 , are used for storing values used by several
registers. These registers include an 8-byte backdoor key, NVBACKKEY, which can be used to gain
access to secure memory resources. During reset events, the contents of NVPROT and NVOPT in the
reserved flash memory are transferred into corresponding FPROT and FOPT registers in the high-page
registers area to control security and block protection options.
Locations 0xFFAE and 0xFFAF are reserved for ICS FTRIM and ICS TRIM values respectively. These
locations are left blank at the factory. Third party tools can program these locations with the trim values.
User can copy these values to corresponding ICS registers to get ICS trimmed clock frequency
Provided the key enable (KEYEN) bit is 1, the 8-byte comparison key can be used to temporarily
disengage memory security. This key mechanism can be accessed only through user code running in secure
memory. (A security key cannot be entered directly through background debug commands.)
This security
key can be disabled completely by programming the KEYEN bit to 0. If the security key is disabled, the
only way to disengage security is by mass erasing the flash if needed (normally through the background
0x186D PTHSE PTHSE7 PTHSE6 PTHSE5 PTHSE4 PTHSE3 PTHSE2 PTHSE1 PTHSE0
0x186E PTHDS PTHDS7 PTHDS6 PTHDS5 PTHDS4 PTHDS3 PTHDS2 PTHDS1 PTHDS0
0x186F Reserved — — — — — — — —
0x1870 MTIMSC TOF TOIE TRST TSTP 0 0 0 0
0x1871 MTIMCLK 0 0 CLKS PS
0x1872 MTIMCNT COUNT
0x1873 MTIMMOD MOD
0x1874 PTIPE — — PTIPE5 PTIPE4 PTIPE3 PTIPE2 PTIPE1 PTIPE0
0x1875 PTISE — — PTISE5 PTISE4 PTISE3 PTISE2 PTISE1 PTISE0
0x1876 PTIDS — — PTIDS5 PTIDS4 PTIDS3 PTIDS2 PTIDS1 PTIDS0
0x1877 Reserved — — — — — — — —
0x1878 KBISC 0 0 0 0 KBF KBACK KBIE KBMOD
0x1879 KBIPE KBIPE7 KBIPE6 KBIPE5 KBIPE4 KBIPE3 KBIPE2 KBIPE1 KBIPE0
0x187A KBIES KBEDG7 KBEDG6 KBEDG5 KBEDG4 KBEDG3 KBEDG2 KBEDG1 KBEDG0
Table 4-5. Reserved Flash Memory Addresses
Address Register Name Bit 7 6 5 4 3 2 1 Bit 0
0xFFB0 –
0xFFB7
NVBACKKEY
8-Byte Comparison Key
0xFFB8 –
0xFFBC
Reserved
—
— —
— —
— —
— —
— —
— —
— —
—
0xFFBD NVPROT
FPS FPDIS
0xFFBE
Reserved
— — — — — — — —
0xFFBF NVOPT
KEYEN FNORED 0 0 0 0 SEC
Table 4-4. High-Page Register Summary (Sheet 3 of 3)
Address Register Name Bit 7 6 5 4 3 2 1 Bit 0