MC9S08JM60_09 Datasheet, PDF (50/388 Pages) Freescale Semiconductor, Inc – HCS08 Microcontrollers

Chapter 4 Memory
Table 4-3. High-Page Register Summary (Sheet 3 of 3)
Address Register Name Bit 7
6
0x1857 Reserved
—
—
0x1858 PTGPE
—
—
0x1859 PTGSE
—
—
0x185A PTGDS
—
—
0x185B– Reserved
0x185F
—
—
1 _{This reserved bit must always be written to 0.}
5
—
PTGPE5
PTGSE5
PTGDS5
4
—
PTGPE4
PTGSE4
PTGDS4
3
—
PTGPE3
PTGSE3
PTGDS3
2
—
PTGPE2
PTGSE2
PTGDS2
1
—
PTGPE1
PTGSE1
PTGDS1
Bit 0
—
PTGPE0
PTGSE0
PTGDS0
—
—
—
—
—
—
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.
Table 4-4. Nonvolatile Register Summary
Address Register Name
0xFFAE Reserved for
storage of FTRIM
0xFFAF Res. for storage of
MCGTRIM
0xFFB0–
0xFFB7
NVBACKKEY
0xFFB8–
0xFFBC
Reserved
0xFFBD NVPROT
0xFFBE Reserved
0xFFBF NVOPT
Bit 7
0
—
FPS7
—
KEYEN
6
0
—
FPS6
—
FNORED
5
4
3
2
0
0
0
0
TRIM
8-Byte Comparison Key
—
FPS5
—
0
—
FPS4
—
0
—
FPS3
—
0
—
FPS2
—
0
1
Bit 0
0
FTRIM
—
FPS1
—
SEC01
—
FPDIS
—
SEC00
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
debug interface) and verifying that flash is blank. To avoid returning to secure mode after the next reset,
program the security bits (SEC01:SEC00) to the unsecured state (1:0).
4.3 RAM (System RAM)
The MC9S08JM60 series includes static RAM. The locations in RAM below 0x0100 can be accessed
using the more efficient direct addressing mode, and any single bit in this area can be accessed with the bit
manipulation instructions (BCLR, BSET, BRCLR, and BRSET). Locating the most frequently accessed
program variables in this area of RAM is preferred.
MC9S08JM60 Series Data Sheet, Rev. 3
50
Freescale Semiconductor