EDLSR, External Debug Lock Status Register

The EDLSR characteristics are:

Purpose

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

This register is part of the Debug registers functional group.

Usage constraints

This register is accessible as follows:

Default
RO

Configuration

EDLSR is in the Debug power domain. Some or all RW fields of this register have defined reset values. These apply only on an External debug reset. The register is not affected by a Warm reset and is not affected by a Cold reset.

If OPTIONAL memory-mapped access to the external debug interface is supported then an OPTIONAL Software Lock can be implemented as part of CoreSight compliance.

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
0

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

1

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

When this register has an architecturally-defined reset value, 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
0

Software Lock not implemented or not memory-mapped access.

1

Software Lock implemented and memory-mapped access.

Accessing the EDLSR

EDLSR can be accessed through a memory-mapped access to the external debug interface:

ComponentOffset
Debug 0xFB4



02/05/2017 15:43

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