PXD10RM Datasheet, PDF (111/1332 Pages) Freescale Semiconductor, Inc – PXD10 Microcontroller

4.1.4.2 Change Lock Settings
To change the setting whether an address is locked or unlocked the corresponding SLBRn.SLBm bit needs
to be changed. This can be done using the following methods:
• Modify the SLBRn.SLBm directly by writing to area #4
• Set the SLBRn.SLBm bit(s) by writing to the mirror module space (area #3)
Both methods are explained in the following sections.
4.1.4.2.1 Change Lock Settings Directly Via Area #4
In memory area #4 the lock bits are located. They can be modified by writing to them. Each SLBRn.SLBm
bit has a mask bit SLBRn.WEm which protects it from being modified. This masking makes
clear-modify-write operations unnecessary.
Figure 4-6 shows two modification examples. In the left example there is a write access to the SLBRn
register specifying a mask value which allows modification of all SLBRn.SLBm bits. The example on the
right specifies a mask which only allows modification of the bits SLBRn.SLB[3:1].
to SLB0 to SLB1 to SLB2 to SLB3 write data
to SLB0 to SLB1 to SLB2 to SLB3 write data
1
1
1
1 SLBRn.WE[3:0]
0
1
1
1 SLBRn.WE[3:0]
change allowed
SLB0 SLB1 SLB2 SLB3 SLBRn.SLB[3:0]
change allowed
SLB0 SLB1 SLB2 SLB3 SLBRn.SLB[3:0]
Figure 4-6. Change Lock Settings Directly Via Area #4
Figure 4-6 showed four registers that can be protected 8-bit wise. In Figure 4-7 registers with 16-bit
protection and in Figure 4-8 registers with 32-bit protection are shown:
to SLB0 to SLB1 to SLB2 to SLB3 write data
to SLB0 to SLB1 to SLB2 to SLB3 write data
1
X
1
X SLBRn.WE[3:0]
1
X
0
0 SLBRn.WE[3:0]
update lock bits
SLB0 SLB1 SLB2 SLB3 SLBR
update lock bits
SLB0 SLB1 SLB2 SLB3 SLBR
Figure 4-7. Change Lock Settings for 16-bit Protected Addresses
On the right side of Figure 4-7 it is shown that the data written to SLBRn.SLB[0] is automatically written
to SLBRn.SLB[1] also. This is done as the address reflected by SLBRn.SLB[0] is protected 16-bit wise.
PXD10 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
4-7
Preliminary—Subject to Change Without Notice