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Translation Table Base Register 1

The TTBR1_EL1 characteristics are:


Holds the base address of translation table 1, and information about the memory it occupies. This is one of the translation tables for the stage 1 translation of memory accesses at EL0 and EL1.

Usage constraints

This register is accessible as follows:








(SCR.NS = 1)


(SCR.NS = 0)


Any of the fields in this register are permitted to be cached in a TLB.


TTBR1_EL1 is architecturally mapped to AArch32 register TTBR1 (NS). See Translation Table Base Register 1.


TTBR1_EL1 is a 64-bit register.

Figure 4.41 shows the TTBR1_EL1 bit assignments.

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Table 4.85 shows the TTBR1_EL1 bit assignments.

Table 4.85. TTBR1_EL1 bit assignments
Bits Name Function
[63:48] ASID

An ASID for the translation table base address. The TCR_EL1.A1 field selects either TTBR0_EL1.ASID or TTBR1_EL1.ASID.

[47:0] BADDR[47:x]

Translation table base address, bits[47:x]. Bits [x-1:0] are res0.

x is based on the value of TCR_EL1.T0SZ, the stage of translation, and the memory translation granule size.

For instructions on how to calculate it, see the ARM® Architecture Reference Manual ARMv8, for ARMv8-A architecture profile.

The value of x determines the required alignment of the translation table, that must be aligned to 2x bytes.

If bits [x-1:0] are not all zero, this is a misaligned Translation Table Base Address. Its effects are constrained unpredictable, where bits [x-1:0] are treated as if all the bits are zero. The value read back from those bits is the value written.

To access the TTBR1_EL1:

MRS <Xt>, TTBR1_EL1 ; Read TTBR1_EL1 into Xt
MSR TTBR1_EL1, <Xt> ; Write Xt to TTBR1_EL1
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