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# EDDEVARCH, External Debug Device Architecture register

The EDDEVARCH characteristics are:

## Purpose

Identifies the programmers' model architecture of the external debug component.

## Configuration

It is IMPLEMENTATION DEFINED whether EDDEVARCH is implemented in the Core power domain or in the Debug power domain.

Implementation of this register is OPTIONAL.

If ARMv8.3-DoPD is implemented, this register is in the Core power domain. If ARMv8.3-DoPD is not implemented, this register is in the Debug power domain.

## Attributes

EDDEVARCH is a 32-bit register.

## Field descriptions

The EDDEVARCH bit assignments are:

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
ARCHITECT | PRESENT | REVISION | ARCHVER | ARCHPART

#### ARCHITECT, bits [31:21]

Defines the architecture of the component. For debug, this is Arm Limited.

Bits [31:28] are the JEP106 continuation code, 0x4.

Bits [27:21] are the JEP106 ID code, 0x3B.

#### PRESENT, bit [20]

When set to 1, indicates that the DEVARCH is present.

This field is 1 in Armv8.

#### REVISION, bits [19:16]

Defines the architecture revision. For architectures defined by Arm this is the minor revision.

For debug, the revision defined by Armv8-A is 0x0.

All other values are reserved.

#### ARCHVER, bits [15:12]

Defines the architecture version of the component. This is the same value as ID_AA64DFR0_EL1.DebugVer and DBGDIDR.Version. The defined values of this field are:

ARCHVER | Meaning
--- | ---
0b0110 | Armv8.0 Debug architecture.
0b0111 | Armv8.0 Debug architecture with Virtualization Host Extensions.
0b1000 | Armv8.2 Debug architecture.
0b1001 | Armv8.4 Debug architecture.

ARMv8.4-Debug adds the functionality indicated by the value 0b1001. ARMv8.2-Debug adds the functionality indicated by the value 0b1000. If ARMv8.1-VHE is not implemented, the only permitted value is 0b0110.

The fields ARCHVER and ARCHPART together form the field ARCHID, so that ARCHVER is ARCHID[15:12].

#### ARCHPART, bits [11:0]

ARCHPART | Meaning
--- | ---
0xA15 | The part number of the Armv8-A debug component.

The fields ARCHVER and ARCHPART together form the field ARCHID, so that ARCHPART is ARCHID[11:0].

## Accessing the EDDEVARCH

#### EDDEVARCH can be accessed through the external debug interface:

Component | Offset | Instance
--- | --- | ---
Debug | 0xFBC | EDDEVARCH

This interface is accessible as follows:

- When ARMv8.3-DoPD is not implemented or IsCorePowered() access to this register is RO.
- Otherwise access to this register returns an Error.

AArch32 Registers | AArch64 Registers | AArch32 Instructions | AArch64 Instructions | Index by Encoding | External Registers | External Registers by Offset | Registers by Functional Group | Proprietary Notice

27/03/2019 21:59; e5e4db499bf9867a4b93324c4dbac985d3da9376

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