CNTVCT, Counter-timer Virtual Count register

The CNTVCT characteristics are:

Purpose

Holds the 64-bit virtual count value. The virtual count value is equal to the physical count value visible in CNTPCT minus the virtual offset visible in CNTVOFF.

This register is part of the Generic Timer registers functional group.

Configuration

There is one instance of this register that is used in both Secure and Non-secure states.

AArch32 System register CNTVCT is architecturally mapped to AArch64 System register CNTVCT_EL0.

The value of this register is the same as the value of CNTPCT in the following conditions:

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

This register can be read using MRRC with the following syntax:

MRRC <syntax>

This syntax uses the following encoding in the System instruction encoding space:

<syntax> opc1coprocCRm
p15, 1, <Rt>, <Rt2>, c14000111111110

Accessibility

The register is accessible as follows:

Control Accessibility
E2HTGENSEL0EL1EL2EL3
xx0RORO n/a RO
x01RORORORO
x11RO n/a RORO

This table applies to all instructions that can access this register.

Traps and enables

For a description of the prioritization of any generated exceptions, see section G1.11.2 (Exception priority order) in the ARM® Architecture Reference Manual, ARMv8, for ARMv8-A architecture profile for exceptions taken to AArch32 state, and section D1.13.2 (Synchronous exception prioritization) for exceptions taken to AArch64 state. Subject to the prioritization rules, the following traps and enables are applicable when accessing this register.

When HCR_EL2.E2H==0 :

When EL2 is implemented and is using AArch64 and SCR_EL3.NS==1 && HCR_EL2.E2H==1 && HCR_EL2.TGE==0 :

When EL2 is implemented and is using AArch64 and SCR_EL3.NS==1 && HCR_EL2.E2H==1 && HCR_EL2.TGE==1 :




28/09/2017 08:24

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