System Control
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
4-231
ID021414
Non-Confidential
To access the TTBCR:
MRC p15,0,<Rt>,c2,c0,0 ; Read TTBR0 into Rt
MCR p15,0,<Rt>,c2,c0,0 ; Write Rt to TTBR0
[22]
A1
Selects whether TTBR0 or TTBR1 defines the ASID:
0
TTBR0.ASID defines the ASID.
1
TTBR1.ASID defines the ASID.
[21:19]
-
Reserved,
RES
0.
[18:16]
T1SZ
The size offset of the memory region addressed by TTBR1. The region size is 2
32-T1SZ
bytes.
Resets to 0.
[15:14]
-
Reserved,
RES
0.
[13:12]
SH0
Shareability attribute for memory associated with translation table walks using TTBR0:
0b00
Non-shareable.
0b10
Outer Shareable.
0b11
Inner Shareable.
Other values are reserved.
Resets to 0.
[11:10]
ORGN0
Outer cacheability attribute for memory associated with translation table walks using TTBR0:
0b00
Normal memory, Outer Non-cacheable.
0b01
Normal memory, Outer Write-Back Write-Allocate Cacheable.
0b10
Normal memory, Outer Write-Through Cacheable.
0b11
Normal memory, Outer Write-Back no Write-Allocate Cacheable.
Resets to 0.
[9:8]
IRGN0
Inner cacheability attribute for memory associated with translation table walks using TTBR0:
0b00
Normal memory, Inner Non-cacheable.
0b01
Normal memory, Inner Write-Back Write-Allocate Cacheable.
0b10
Normal memory, Inner Write-Through Cacheable.
0b11
Normal memory, Inner Write-Back no Write-Allocate Cacheable.
Resets to 0.
[7]
EPD0
Translation table walk disable for translations using TTBR0. This bit controls whether a translation table walk
is performed on a TLB miss, for an address that is translated using TTBR0:
0
Perform translation table walks using TTBR0.
1
A TLB miss on an address that is translated using TTBR0 generates a Translation fault. No
translation table walk is performed.
[6:3]
-
Reserved,
RES
0.
[2:0]
T0SZ
The size offset of the memory region addressed by TTBR0. The region size is 2
32-T0SZ
bytes.
Resets to 0.
Table 4-211 TTBCR bit assignments, TTBCR.EAE is 1 (continued)
Bits
Name
Function