CNTV_CTL, Counter-timer Virtual Timer Control

The CNTV_CTL characteristics are:

Purpose

Control register for the virtual timer.

Configuration

It is IMPLEMENTATION DEFINED whether CNTV_CTL is implemented in the Core power domain or in the Debug power domain.

For more information, see 'Power and reset domains for the system level implementation of the Generic Timer'.

Attributes

CNTV_CTL is a 32-bit register.

Field descriptions

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
RES0																													ISTATUS	IMASK	ENABLE

Bits [31:3]

Reserved, RES0.

ISTATUS, bit [2]

The status of the timer. This bit indicates whether the timer condition is met:

ISTATUS	Meaning
0b0	Timer condition is not met.
0b1	Timer condition is met.

When the value of the ENABLE bit is 1, ISTATUS indicates whether the timer condition is met. ISTATUS takes no account of the value of the IMASK bit. If the value of ISTATUS is 1 and the value of IMASK is 0 then the timer interrupt is asserted.

When the value of the ENABLE bit is 0, the ISTATUS field is UNKNOWN.

The reset behavior of this field is:

On a Timer reset, this field resets to an architecturally UNKNOWN value.

Access to this field is RO.

IMASK, bit [1]

Timer interrupt mask bit. Permitted values are:

IMASK	Meaning
0b0	Timer interrupt is not masked by the IMASK bit.
0b1	Timer interrupt is masked by the IMASK bit.

For more information, see the description of the ISTATUS bit.

The reset behavior of this field is:

On a Timer reset, this field resets to an architecturally UNKNOWN value.

ENABLE, bit [0]

Enables the timer. Permitted values are:

ENABLE	Meaning
0b0	Timer disabled.
0b1	Timer enabled.

Setting this bit to 0 disables the timer output signal, but the timer value accessible from CNTV_TVAL continues to count down.

Note

Disabling the output signal might be a power-saving option.

The reset behavior of this field is:

On a Timer reset, this field resets to an architecturally UNKNOWN value.

Accessing CNTV_CTL

CNTV_CTL can be implemented in any implemented CNTBaseN frame that has virtual timer capability, and in the corresponding CNTEL0BaseN frame.

'CNTCTLBase status and control fields for the CNTBaseN and CNTEL0BaseN frames' 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 supports the Realm Management Extension, whether the CNTBaseN frame, and any corresponding CNTEL0BaseN frame, is accessible by Root and Realm accesses.
For an implementation that recognizes two Security states, whether the CNTBaseN frame, and any corresponding CNTEL0BaseN frame, is accessible by Non-secure accesses. The CNTBaseN frame is always accessible by Secure accesses.

For an implemented CNTBaseN frame that has virtual timer capability:

CNTV_CTL is accessible in that frame if the value of CNTACR<n>.RWVT is 1.
Otherwise, the CNTV_CTL address in that frame is RAZ/WI.

For an implemented CNTEL0BaseN frame:

CNTV_CTL is accessible in that frame if both:
- CNTV_CTL is accessible in the corresponding CNTBaseN frame:
- The value of CNTEL0ACR.EL0VTEN is 1.
Otherwise, the CNTV_CTL address in that frame is RAZ/WI.

CNTV_CTL can be accessed through the memory-mapped interfaces:

Component	Frame	Offset	Instance
Timer	CNTBaseN	0x03C	CNTV_CTL

Accesses on this interface are RW.

Component	Frame	Offset	Instance
Timer	CNTEL0BaseN	0x03C	CNTV_CTL

Accesses on this interface are RW.

26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6