MPC5604B/C Microcontroller Reference Manual, Rev. 8
Freescale Semiconductor 749
Figure 29-9. 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 29-6).
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 29-6).
Figure 29-10 shows an example where some addresses are protected and some are not:
Figure 29-10. Enable Locking for Protected and Unprotected Addresses
In the example in Figure 29-10 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.
29.6.2.3 Write protection for locking bits
Changing the locking bits through any of the procedures mentioned in Section 29.6.2.1, Change lock
settings directly via area #4 and Section 29.6.2.2, 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.
SLBR2
WE[3:0]
00000000
SLB[3:0]
16-bit write to address 0x0008
no change
write to
MR[9:8]
SLBR2
WE[3:0]
00001100
SLB[3:0]
16-bit write to address 0x2008
set lock bits
write to
MR[9:8]
SLBR3
WE[3:0]
00000000
SLB[3:0]
Before write access
SLBR3
WE[3:0]
00000011
SLB[3:0]
32-bit write to address 0x200C
set lock bits
write to
MR[15:12]
After
write access
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