NXP Semiconductors MPC5605BK, Reference Manual, Page: 903 / 964

Chapter 32 Register Protection
MPC5606BK Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 903
Figure 32-9. Enable locking via mirror module space (Area #3)
When writing to address 0x0008 the registers MR9 and MR8 in the protected module are updated. The
corresponding lock bits remain unchanged (left part of
Figure 32-6 ).
When writing to address 0x2008 the registers MR9 and MR8 in the protected module are updated. The
corresponding lock bits SLBR2.SLB[1:0] are set while the lock bits SLBR2.SLB[3:2] remain unchanged
(right part of
Figure 32-6 ).
Figure 32-10 shows an example where some addresses are protected and some are not:
Figure 32-10. Enable locking for protected and unprotected addresses
In the example in Figure 32-10 addresses 0x0C and 0x0D are unprotected. Therefore their corresponding
lock bits SLBR3.SLB[1:0] are always 0b0 (shown in bold). When doing a 32-bit write access to address
0x200C only lock bits SLBR3.SLB[3:2] are set while bits SLBR3.SLB[1:0] stay 0b0.
NOTE
Lock bits can only be set via writes to the mirror module space. Reads from
the mirror module space will not change the lock bits.
32.6.2.3 Write protection for locking bits
Changing the locking bits through any of the procedures mentioned in Section 32.6.2.1, Change lock
settings directly via area #4 and Section 32.6.2.2, Enable locking via mirror module space (area #3) is only
possible as long as the bit GCR.HLB is cleared. Once this bit is set, the locking bits can no longer be
modified until there is a system reset.
SLBR 2
WE[3:0]
0 0 0 0 0 0 0 0
SLB[3:0]
16-bit write to address 0x0008
no change
write to
MR[9:8]
SLBR 2
WE[3:0]
0 0 0 0 1 1 0 0
SLB[3:0]
16-bit write to address 0x2008
set lock bits
write to
MR[9:8]
SLBR 3
WE[3:0]
0 0 0 0 0 0 0 0
SLB[3:0]
Before write access
SLBR 3
WE[3:0]
0 0 0 0 0 0 1 1
SLB[3:0]
32-bit write to address 0x200C
set lock bits
write to
MR[15:12]
After
write access