Datasheet

ManualsBrandsNXP SEMICONDUCTORS ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller QFP 44 (10x10) 8-Bit 40 MHz I/O number 36

Memory

MC9S08GT16A/GT8A Data Sheet, Rev. 1

Freescale Semiconductor 47

Nonvolatile FLASH registers, shown in Table 4-4, are located in the FLASH memory. These registers

include an 8-byte backdoor key which optionally can be used to gain access to secure memory resources.

During reset events, the contents of NVPROT and NVOPT in the nonvolatile register area of the FLASH

memory are transferred into corresponding FPROT and FOPT working registers in the high-page registers

to control security and block protection options.

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

0x1811 DBGCAL

Bit 7 654321Bit 0

0x1812 DBGCBH

Bit 15 14 13 12 11 10 9 Bit 8

0x1813 DBGCBL

Bit 7 654321Bit 0

0x1814 DBGFH

Bit 15 14 13 12 11 10 9 Bit 8

0x1815 DBGFL

Bit 7 654321Bit 0

0x1816 DBGC

DBGEN ARM TAG BRKEN RWA RWAEN RWB RWBEN

0x1817 DBGT

TRGSEL BEGIN 0 0 TRG3 TRG2 TRG1 TRG0

0x1818 DBGS

AF BF ARMF 0 CNT3 CNT2 CNT1 CNT0

0x1819–

0x181F

Reserved

—

0x1820 FCDIV

DIVLD PRDIV8 DIV5 DIV4 DIV3 DIV2 DIV1 DIV0

0x1821 FOPT

KEYEN FNORED 0 0 0 0 SEC01 SEC00

0x1822 Reserved

— — — — — — — —

0x1823 FCNFG

0 0 KEYACC 0 0 0 0 0

0x1824 FPROT

FPS7 FPS6 FPS5 FPS4 FPS3 FPS2 FPS1 FPDIS

0x1825 FSTAT

FCBEF FCCF FPVIOL FACCERR 0 FBLANK 0 0

0x1826 FCMD

FCMD7 FCMD6 FCMD5 FCMD4 FCMD3 FCMD2 FCMD1 FCMD0

0x1827–

0x182B

Reserved

—

Table 4-4. Nonvolatile Register Summary

Address Register Name Bit 7 654321Bit 0

0xFFB0 –

0xFFB7

NVBACKKEY

8-Byte Comparison Key

0xFFB8 –

0xFFBC

Reserved

—

0xFFBD NVPROT

FPS7 FPS6 FPS5 FPS4 FPS3 FPS2 FPS1 FPDIS

0xFFBE NVICGTRM

NVICGTRM is the factory trim value. This value must be copied to ICGTRM in user code.