The CNTV_CVAL characteristics are:
Holds the compare value for the virtual timer.
This register is part of the Generic Timer registers functional group.
There is one instance of this register that is used in both Secure and Non-secure states.
AArch32 System register CNTV_CVAL is architecturally mapped to AArch64 System register CNTV_CVAL_EL0.
RW fields in this register reset to architecturally UNKNOWN values.
CNTV_CVAL is a 64-bit register.
The CNTV_CVAL bit assignments are:
63 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 40 | 39 | 38 | 37 | 36 | 35 | 34 | 33 | 32 |
CompareValue | |||||||||||||||||||||||||||||||
CompareValue | |||||||||||||||||||||||||||||||
31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
Holds the EL1 virtual timer CompareValue.
When CNTV_CTL.ENABLE is 1, the timer condition is met when (CNTVCT - CompareValue) is greater than zero. This means that CompareValue acts like a 64-bit upcounter timer. When the timer condition is met:
When CNTV_CTL.ENABLE is 0, the timer condition is not met, but CNTVCT continues to count.
This register can be read using MRRC with the following syntax:
MRRC <syntax>
This register can be written using MCRR with the following syntax:
MCRR <syntax>
This syntax uses the following encoding in the System instruction encoding space:
<syntax> | opc1 | coproc | CRm |
---|---|---|---|
p15, 3, <Rt>, <Rt2>, c14 | 0011 | 1111 | 1110 |
The register is accessible as follows:
Control | Accessibility | |||||
---|---|---|---|---|---|---|
E2H | TGE | NS | EL0 | EL1 | EL2 | EL3 |
x | x | 0 | RW | RW | n/a | RW |
0 | 0 | 1 | RW | RW | RW | RW |
0 | 1 | 1 | RW | n/a | RW | RW |
1 | 0 | 1 | RW | RW | n/a | n/a |
1 | 1 | 1 | CNTHV_CVAL | n/a | n/a | n/a |
This table applies to all instructions that can access this register.
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 :
If CNTKCTL_EL1.EL0VTEN==0, accesses to this register from EL0 are trapped to EL1.
If CNTKCTL.PL0VTEN==0, accesses to this register from EL0 are trapped to Undefined mode.
When EL2 is implemented and is using AArch64 and SCR_EL3.NS==1 && HCR_EL2.E2H==1 && HCR_EL2.TGE==0 :
If CNTKCTL_EL1.EL0VTEN==0, Non-secure accesses to this register from EL0 are trapped to EL1.
If CNTKCTL.PL0VTEN==0, Non-secure accesses to this register from EL0 are trapped to Undefined mode.
When EL2 is implemented and is using AArch64 and SCR_EL3.NS==1 && HCR_EL2.E2H==1 && HCR_EL2.TGE==1 :
If CNTHCTL_EL2.EL0VTEN==0, Non-secure accesses to this register from EL0 are trapped to EL2.
18/04/2017 17:00
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