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EDPIDR4, External Debug Peripheral Identification Register 4

The EDPIDR4 characteristics are:


Provides information to identify an external debug component.

For more information see 'About the Peripheral identification scheme' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile, section H8 (About the External Debug Registers).


It is IMPLEMENTATION DEFINED whether EDPIDR4 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.

This register is required for CoreSight compliance.


EDPIDR4 is a 32-bit register.

Field descriptions

The EDPIDR4 bit assignments are:


Bits [31:8]

Reserved, RES0.

SIZE, bits [7:4]

Size of the component. RAZ. Log2 of the number of 4KB pages from the start of the component to the end of the component ID registers.

DES_2, bits [3:0]

Designer, JEP106 continuation code, least significant nibble. For Arm Limited, this field is 0b0100.

Accessing the EDPIDR4

EDPIDR4 can be accessed through the external debug interface:


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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