Freescale Semiconductor MPC5604B - Functional Description

MPC5604B/C Microcontroller Reference Manual, Rev. 8
746 Freescale Semiconductor
NOTE
The GCR.UAA bit has no effect on the allowed access modes for the
registers in the Register Protection module.
29.6 Functional description
29.6.1 General
This module provides a generic register (address) write-protection mechanism. The protection size can be:
• 32-bit (address == multiples of 4)
• 16-bit (address == multiples of 2)
• 8-bit (address == multiples of 1)
• unprotected (address == multiples of 1)
Which addresses are protected and the protection size depend on the SoC and/or module. Therefore this
section can just give examples for various protection configurations.
For all addresses that are protected there are SLBRn.SLBm bits that specify whether the address is locked.
When an address is locked it can be read but not written in any mode (supervisor/normal). If an address is
unprotected the corresponding SLBRn.SLBm bit is always 0b0 no matter what software is writing to.
29.6.2 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.
Table 29-4. GCR field descriptions
Field Description
HLB Hard Lock Bit.
This register can not be cleared once it is set by software. It can only be cleared by a system reset.
1 All SLB bits are write protected and can not be modified
0 All SLB bits are accessible and can be modified.
UAA User Access Allowed.
1 The registers in the module under protection can be accessed in the mode defined for the module
registers without any additional restrictions.
0 The registers in the module under protection can only be written in supervisor mode. All write
accesses in non-supervisor mode are not executed and a transfer error is issued. This access
restriction is in addition to any access restrictions imposed by the protected IP module.