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CNTVCT, Counter-timer Virtual Count

The CNTVCT characteristics are:

Purpose

Holds the 64-bit virtual count value.

Configuration

The power domain of CNTVCT is IMPLEMENTATION DEFINED.

For more information see 'Power and reset domains for the system level implementation of the Generic Timer' in Chapter I1 of the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile.

Attributes

CNTVCT is a 64-bit register.

Field descriptions

The CNTVCT bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
Virtual count value
Virtual count value
313029282726252423222120191817161514131211109876543210

Bits [63:0]

Virtual count value.

Accessing the CNTVCT

CNTVCT can be implemented in any implemented CNTBaseN frame, and in the corresponding CNTEL0BaseN frame, as a RO register.

'CNTCTLBase status and control fields for the CNTBaseN and CNTEL0BaseN frames' in Chapter I1 of the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile describes the status fields that identify whether a CNTBaseN frame is implemented, and for an implemented frame:

  • Whether the CNTBaseN frame has virtual timer capability.
  • Whether the corresponding CNTEL0BaseN frame is implemented.
  • For an implementation that recognizes two Security states, whether the CNTBaseN frame, and any corresponding CNTEL0BaseN frame, is accessible by Non-secure accesses.

For an implemented CNTBaseN frame:

  • CNTVCT is accessible in that frame, as a RO register, if the value of CNTACR<n>.RVCT is 1.
  • Otherwise, the CNTVCT address in that frame is RAZ/WI.

For an implemented CNTEL0BaseN frame:

  • CNTVCT is accessible in that frame if both:
    • CNTVCT is accessible in the corresponding CNTBaseN frame.
    • The value of CNTEL0ACR.EL0VCTEN is 1.
  • Otherwise, the CNTVCT address in that frame is RAZ/WI.

If the implementation supports 64-bit atomic accesses, then the CNTVCT register must be accessible as an atomic 64-bit value.

CNTVCT can be accessed through the memory-mapped interfaces:

ComponentFrameOffsetInstanceRange
TimerCNTBaseN0x008CNTVCT31:0

Access on this interface is RO.

ComponentFrameOffsetInstanceRange
TimerCNTBaseN0x00CCNTVCT63:32

Access on this interface is RO.

ComponentFrameOffsetInstanceRange
TimerCNTEL0BaseN0x008CNTVCT31:0

Access on this interface is RO.

ComponentFrameOffsetInstanceRange
TimerCNTEL0BaseN0x00CCNTVCT63:32

Access on this interface is RO.



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