PXD10RM Datasheet, PDF (113/1332 Pages) Freescale Semiconductor, Inc – PXD10 Microcontroller

16-bit write to address 0x0008 ^{write to}
MR[9:8]
16-bit write to address 0x2008 ^{write to}
MR[9:8]
no change
set lock bits
0 0 0 0 0 0 0 0 SLBR2
0 0 0 0 1 1 0 0 SLBR2
WE[3:0]
SLB[3:0]
WE[3:0] SLB[3:0]
Figure 4-10. 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 4-7).
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 4-7).
Figure 4-11 shows an example where some addresses are protected and some are not:
Before write access
32-bit write to address 0x200C ^{write to}
MR[15:12]
0 0 0 0 0 0 0 0 SLBR3
After
write access
set lock bits
00000011
SLBR3
WE[3:0]
SLB[3:0]
WE[3:0] SLB[3:0]
Figure 4-11. Enable Locking for Protected and Unprotected Addresses
In the example in Figure 4-11 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.
4.1.4.2.3 Write Protection for Locking Bits
Changing the locking bits through any of the procedures mentioned in Section 4.1.4.2.1, Change Lock
Settings Directly Via Area #4, and Section 4.1.4.2.2, 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 was a system reset.
4.1.4.3 Access Errors
The protection module generates transfer errors under several circumstances. For the area definition refer
to Figure 4-2.
1. If accessing area #1 or area #3, the protection module will pass on any access error from the
underlying Module under Protection.
PXD10 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
4-9
Preliminary—Subject to Change Without Notice