System Control Coprocessor
ARM DDI 0301H Copyright © 2004-2009 ARM Limited. All rights reserved. 3-95
ID012310 Non-Confidential, Unrestricted Access
The Instruction TCM Non-secure Control Access Register is:
•in CP15 c9
• a 32-bit read/write register in the Secure world only
• accessible in privileged modes only.
If the processor is configured to have 2 Instruction TCMs, each TCM has a separate Instruction
TCM Non-secure Control Access Register. The TCM Selection Register determines the register
in use.
Figure 3-53 shows the bit arrangement for the Instruction TCM Non-secure Control Access
Register.
Figure 3-53 Instruction TCM Non-secure Control Access Register format
Table 3-91 lists how the bit values correspond with the register functions.
Table 3-92 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.
31 10
SBZ
NS access
Table 3-91 Instruction TCM Non-secure Control Access Register bit functions
Bits Field name Function
[31:1] - UNP/SBZ.
[0] NS access Makes Instruction TCM invisible to the Non-secure world and makes TCM data Secure.
0 = Instruction TCM Region Register only accessible in the Secure world. Instruction 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 = Instruction TCM Region Register accessible in the Secure and Non-secure worlds.
Instruction 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 3-92 Effects of NS items for instruction 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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