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EDDEVID, External Debug Device ID register 0

The EDDEVID characteristics are:

Purpose

Provides extra information for external debuggers about features of the debug implementation.

Configuration

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

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

EDDEVID is a 32-bit register.

Field descriptions

The EDDEVID bit assignments are:

313029282726252423222120191817161514131211109876543210
0000AuxRegs0000000000000000DebugPowerPCSample

Bits [31:28]

Reserved, RES0.

AuxRegs, bits [27:24]

Indicates support for Auxiliary registers. Permitted values for this field are:

AuxRegsMeaning
0b0000

None supported.

0b0001

Support for External Debug Auxiliary Control Register, EDACR.

All other values are reserved.

Bits [23:8]

Reserved, RES0.

DebugPower, bits [7:4]

When ARMv8.3-DoPD is implemented:

Indicates support for the Armv8.3 debug over powerdown feature. Defined values of this field are:

DebugPowerMeaning
0b0000

Armv8.3 debug over powerdown not implemented. Registers in the external debug interface register map are implemented in a mix of the Debug and Core power domains.

0b0001

Armv8.3 debug over powerdown implemented. All registers in the external debug interface register map are implemented in the Core power domain.

ARMv8.3-DoPD implements the functionality added by the value 0b0001.

All other values are reserved.


Otherwise:

Reserved, RES0.

PCSample, bits [3:0]

Indicates the level of PC Sample-based Profiling support using external debug registers. Permitted values of this field are:

PCSampleMeaning
0b0000

PC Sample-based Profiling Extension is not implemented in the external debug registers space.

0b0010

Only EDPCSR and EDCIDSR are implemented. This option is only permitted if EL3 and EL2 are not implemented.

0b0011

EDPCSR, EDCIDSR, and EDVIDSR are implemented.

All other values are reserved.

When ARMv8.2-PCSample is implemented, the only permitted value is 0b0000.

Note

ARMv8.2-PCSample implements the PC Sample-based Profiling Extension in the Performance Monitors register space, as indicated by the value of PMDEVID.PCSample.

Accessing the EDDEVID

EDDEVID can be accessed through the external debug interface:

ComponentOffsetInstance
Debug0xFC8EDDEVID

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.


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