System Control Coprocessor
ARM DDI 0301H Copyright © 2004-2009 ARM Limited. All rights reserved. 3-94
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Table 3-89 lists how the bit values correspond with the register functions.
Table 3-90 lists the effect on TCM operations for different combinations of operating world and
NS bits.
Attempts to write to this register in Secure Privileged mode when CP15SDISABLE is HIGH
result in an Undefined exception, see TrustZone write access disable on page 2-9.
Attempts to access the Data TCM Non-secure Control Access Register in modes other than
Secure privileged result in an Undefined exception.
To use the Data TCM Non-secure Control Access Register read or write CP15 with:
• Opcode_1 set to 0
• CRn set to c9
• CRm set to c1
• Opcode_2 set to 2.
For example:
MRC p15,0,<Rd>,c9,c1,2 ; Read Data TCM Non-secure Control Access Register
MCR p15,0,<Rd>,c9,c1,2 ; Write Data TCM Non-secure Control Access Register
3.2.28 c9, Instruction TCM Non-secure Control Access Register
The purpose of the Instruction TCM Non-secure Control Access Register is to:
• set access permission to the Instruction TCM Region Register
• define instructions in the Instruction TCM as Secure or Non-secure.
Table 3-89 Data TCM Non-secure Control Access Register bit functions
Bits Field name Function
[31:1] - UNP/SBZ.
[0] NS access Makes Data TCM invisible to the Non-secure world and makes TCM data Secure.
0 = Data TCM Region Register only accessible in the Secure world. Data TCM only visible in
the Secure world and only when the NS Attribute in the page table is 0. The reset value is 0.
1 = Data TCM Region Register accessible in the Secure and Non-secure worlds. Data TCM is
visible in the Non-secure world, and also in the Secure world if the NS Attribute in the page table
is 1.
Table 3-90 Effects of NS items for data TCM operation
World
NS
acces
s
NS page
table
Region
visible
Control Data
Secure 0 1 No - -
10 No- -
0 0 Yes Secure privileged only Secure only
1 1 Yes Secure and Non-secure privileged Non-secure only
Non-secure 1 X Yes Secure and Non-secure privileged Non-secure only
0X No- -
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