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EDLSR, External Debug Lock Status Register

The EDLSR characteristics are:

Purpose

Indicates the current status of the software lock for external debug registers.

Configuration

It is IMPLEMENTATION DEFINED whether EDLSR is implemented in the Core power domain or in the Debug power domain. Some or all RW fields of this register have defined reset values, and:

  • The register is not affected by a Warm reset.
  • If the register is implemented in the Core power domain the reset values apply on a Cold reset, and the register is not affected by an External debug reset.
  • If the register is implemented in the Debug power domain the reset values apply on an External debug reset, and the register is not affected by a Cold reset.

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.

EDLSR is RAZ if the Software Lock is not implemented and is RAZ for other accesses to the external debug interface.

The Software Lock provides a lock to prevent memory-mapped writes to the debug registers. Use of this lock mechanism reduces the risk of accidental damage to the contents of the debug registers. It does not, and cannot, prevent all accidental or malicious damage.

Software uses EDLAR to set or clear the lock, and EDLSR to check the current status of the lock.

Attributes

EDLSR is a 32-bit register.

Field descriptions

The EDLSR bit assignments are:

313029282726252423222120191817161514131211109876543210
00000000000000000000000000000nTTSLKSLI

Bits [31:3]

Reserved, RES0.

nTT, bit [2]

Not thirty-two bit access required. RAZ.

SLK, bit [1]

Software Lock status for this component. For an access to LSR that is not a memory-mapped access, or when the Software Lock is not implemented, this field is RES0.

For memory-mapped accesses when the Software Lock is implemented, possible values of this field are:

SLKMeaning
0b0

Lock clear. Writes are permitted to this component's registers.

0b1

Lock set. Writes to this component's registers are ignored, and reads have no side effects.

The following resets apply:

  • If Armv8.3-DoPD is implemented, this register is reset by Cold reset and not affected by External debug reset. If Armv8.3-DoPD is not implemented, this register is reset by External debug reset and not affected by Cold reset.

  • On a reset, this field resets to 1.

SLI, bit [0]

Software Lock implemented. For an access to LSR that is not a memory-mapped access, this field is RAZ. For memory-mapped accesses, the value of this field is IMPLEMENTATION DEFINED. Permitted values are:

SLIMeaning
0b0

Software Lock not implemented or not memory-mapped access.

0b1

Software Lock implemented and memory-mapped access.

Accessing the EDLSR

EDLSR can be accessed through the memory-mapped interfaces:

ComponentOffsetInstance
Debug0xFB4EDLSR

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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