EDPCSR | Jon's Arm Reference

This register is present only when FEAT_PCSRv8 is implemented and FEAT_PCSRv8p2 is not implemented. Otherwise, direct accesses to EDPCSR are RES0.

EDPCSR[63:32] and EDPCSR[31:0] are accessed at 32-bit memory mapped addresses that are not contiguous.

If FEAT_VHE is implemented, the format of this register differs depending on the value of EDSCR.SC2.

Implemented only if the OPTIONAL PC Sample-based Profiling Extension is implemented in the external debug registers space.

Attributes

Field descriptions

When FEAT_VHE is not implemented or EDSCR.SC2 == 0:

Bits [63:32]

PC Sample high word, EDPCSRhi. If EDVIDSR.HV == 0 then this field is RAZ, otherwise bits [63:32] of the sampled instruction address value. The translation regime that EDPCSR samples can be determined from EDVIDSR.{NS,E2,E3}.

The reset behavior of this field is:

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

Bits [31:0]

PC Sample low word. EDPCSRlo, bits[31:0] of the sampled instruction address value.

EDPCSRlo reads as 0xFFFFFFFF when any of the following are true:

The PE is in Debug state.
PC Sample-based profiling is prohibited.

If a branch instruction has retired since the PE left reset state, then the first read of EDPCSR[31:0] is permitted but not required to return 0xFFFFFFFF.

EDPCSRlo reads as an UNKNOWN value when any of the following are true:

The PE is in reset state.
No branch instruction has retired since the PE left reset state, Debug state, or a state where PC Sample-based Profiling is prohibited.
No branch instruction has retired since the last read of EDPCSR[31:0].

For the cases where a read of EDPCSR[31:0] returns 0xFFFFFFFF or an UNKNOWN value, the read has the side-effect of setting EDPCSRhi, EDCIDSR, and EDVIDSR to UNKNOWN values.

Otherwise, a read of EDPCSR[31:0] returns bits [31:0] of the sampled instruction address value and has the side-effect of indirectly writing to EDPCSRhi, EDCIDSR, and EDVIDSR. The translation regime that EDPCSR samples can be determined from EDVIDSR.{NS,E2,E3}.

For a read of EDPCSR[31:0] from the memory-mapped interface, if EDLSR.SLK == 1, meaning the OPTIONAL Software Lock is locked, then the side-effect of the access does not occur and EDPCSRhi, EDCIDSR, and EDVIDSR are unchanged.

The reset behavior of this field is:

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

When FEAT_VHE is implemented and EDSCR.SC2 == 1:

NS, bit [63]

Non-secure state sample. Indicates the Security state that is associated with the most recent EDPCSR sample or, when it is read as a single atomic 64-bit read, the current EDPCSR sample. The translation regime that EDPCSR samples can be determined from EDPCSR.{NS,EL}.

If EL3 is not implemented, this bit indicates the Effective value of SCR.NS.

NS	Meaning
0b0	Sample is from Secure state.
0b1	Sample is from Non-secure state.

The reset behavior of this field is:

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

EL, bits [62:61]

Exception level status sample. Indicates the Exception level that is associated with the most recent EDPCSR sample or, when it is read as a single atomic 64-bit read, the current EDPCSR sample. The translation regime that EDPCSR samples can be determined from EDPCSR.{NS,EL}.

EL	Meaning
0b00	Sample is from EL0.
0b01	Sample is from EL1.
0b10	Sample is from EL2.
0b11	Sample is from EL3.

The reset behavior of this field is:

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

Bits [60:56]

Bits [55:32]

PC Sample high word, EDPCSRhi. Bits [55:32] of the sampled instruction address value. The translation regime that EDPCSR samples can be determined from EDPCSR.{NS,EL}.

The reset behavior of this field is:

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

Bits [31:0]

PC Sample low word. EDPCSRlo, bits[31:0] of the sampled instruction address value.

EDPCSRlo reads as 0xFFFFFFFF when any of the following are true:

The PE is in Debug state.
PC Sample-based profiling is prohibited.

If a branch instruction has retired since the PE left reset state, then the first read of EDPCSR[31:0] is permitted but not required to return 0xFFFFFFFF.

EDPCSRlo reads as an UNKNOWN value when any of the following are true:

The PE is in reset state.
No branch instruction has retired since the PE left reset state, Debug state, or a state where PC Sample-based Profiling is prohibited.
No branch instruction has retired since the last read of EDPCSR[31:0].

For the cases where a read of EDPCSR[31:0] returns 0xFFFFFFFF or an UNKNOWN value, the read has the side-effect of setting EDPCSRhi, EDCIDSR, and EDVIDSR to UNKNOWN values.

The reset behavior of this field is:

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

Accessing EDPCSR

IMPLEMENTATION DEFINED extensions to external debug might make the value of this register UNKNOWN, see 'Permitted behavior that might make the PC Sample-based profiling registers UNKNOWN'

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
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
PC Sample high word, EDPCSRhi
PC Sample low word

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
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
NS	EL		RES0					PC Sample high word, EDPCSRhi
PC Sample low word

EDPCSR: External Debug Program Counter Sample Register

Purpose

Configuration

Attributes

Field descriptions

When FEAT_VHE is not implemented or EDSCR.SC2 == 0:

Bits [63:32]

Bits [31:0]

When FEAT_VHE is implemented and EDSCR.SC2 == 1:

NS, bit [63]

EL, bits [62:61]

Bits [60:56]

Bits [55:32]

Bits [31:0]

Accessing EDPCSR

EDPCSR can be accessed through the external debug interface: