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TRBBASER_EL1

TRBBASER_EL1, Trace Buffer Base Address Register

The TRBBASER_EL1 characteristics are:

Purpose

Defines the base address for the trace buffer.

Configuration

External register TRBBASER_EL1 bits [63:0] are architecturally mapped to AArch64 System register TRBBASER_EL1[63:0].

TRBBASER_EL1 is in the Core power domain.

This register is present only when FEAT_TRBE_EXT is implemented. Otherwise, direct accesses to TRBBASER_EL1 are RES0.

Attributes

TRBBASER_EL1 is a 64-bit register.

Field descriptions

63	62	61	60	59	58	57	56	55	54	53	52	51	50	49	48	47	46	45	44	43	42	41	40	39	38	37	36	35	34	33	32
31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
BASE
BASE																				RES0

BASE, bits [63:12]

Trace Buffer Base pointer address. (TRBBASER_EL1.BASE << 12) is the address of the first byte in the trace buffer. Bits [11:0] of the Base pointer address are always zero. If the smallest implemented translation granule is not 4KB, then TRBBASER_EL1[N-1:12] are RES0, where N is the IMPLEMENTATION DEFINED value Log₂(smallest implemented translation granule).

The reset behavior of this field is:

On a Cold reset, this field resets to an architecturally UNKNOWN value.

Bits [11:0]

Reserved, RES0.

Accessing TRBBASER_EL1

The PE might ignore a write to TRBBASER_EL1 if any of the following apply:

TRBLIMITR_EL1.E is 1 and the Trace Buffer Unit is using Self-hosted mode.
TRBLIMITR_EL1.XE is 1 and the Trace Buffer Unit is using External mode.

TRBBASER_EL1 can be accessed through the external debug interface:

Component	Offset	Instance
TRBE	0x000	TRBBASER_EL1

Accessible as follows:

When DoubleLockStatus(), or !IsCorePowered(), or OSLockStatus(), or !AllowExternalTraceBufferAccess(addrdesc), accesses to this register generate an error response.
Otherwise, accesses to this register are RW.

2026-03-26 20:27:25, 2026-03_rel