time

Timer for RDTIME Instruction

This CSR does not exist, and access will cause an IllegalInstruction exception.

Shadow of the memory-mapped M-mode CSR mtime.

Privilege mode access is controlled with mcounteren.TM, scounteren.TM, and hcounteren.TM as follows:

mcounteren.TM	scounteren.TM	scounteren.TM	time behavior
S-mode	U-mode	VS-mode	VU-mode
0	-	-	`Illegal Instruction`	`Illegal Instruction`	`Illegal Instruction`	`Illegal Instruction`
1	0	0	read-only	`Illegal Instruction`	`Illegal Instruction`	`Illegal Instruction`
1	1	0	read-only	read-only	`Illegal Instruction`	`Illegal Instruction`
1	0	1	read-only	`Illegal Instruction`	read-only	`Illegal Instruction`
1	1	1	read-only	read-only	read-only	read-only

mcounteren.TM

scounteren.TM

time behavior

S-mode

U-mode

VS-mode

VU-mode

Illegal Instruction

read-only

Illegal Instruction

read-only

Illegal Instruction

read-only

Illegal Instruction

read-only

Illegal Instruction

read-only

Attributes

CSR Address	0xc01
Defining extension	Zicntr, version >= 0
Length	64-bit
Privilege Mode	U

CSR Address

0xc01

Defining extension

Zicntr, version >= 0

Length

64-bit

Privilege Mode

Format

Figure 1. time format

Field Summary

Name Location Type Reset Value

Name	Location	Type	Reset Value
`COUNT`	63:0	RO-H	UNDEFINED_LEGAL

COUNT

63:0

RO-H

UNDEFINED_LEGAL

Fields

`COUNT`

Location: time[63:0]
Description: Reports the current wall-clock time from the timer device.

Alias of the mtime memory-mapped CSR.
Type

RO-H	Read-Only with Hardware update Writes are ignored. Reads reflect a value dynamically generated by hardware.

Reset value: UNDEFINED_LEGAL

Software read

This CSR may return a value that is different from what is stored in hardware.

Pruned
Original

if (mode() == PrivilegeMode::S) {
  raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
} else if (mode() == PrivilegeMode::U) {
  raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
} else if (mode() == PrivilegeMode::VS) {
  if (true && CSR[mcounteren] == 1'b1) {
    raise(ExceptionCode::VirtualInstruction, mode(), $encoding);
  } else {
    raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
  }
} else if (mode() == PrivilegeMode::VU) {
  if ((true) && (CSR[mcounteren].IR == 1'b1)) {
    raise(ExceptionCode::VirtualInstruction, mode(), $encoding);
  } else {
    raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
  }
}
return read_mtime();

if (!TIME_CSR_IMPLEMENTED) {
  unimplemented_csr($encoding);
}
if (mode() == PrivilegeMode::S) {
  if (CSR[mcounteren].TM == 1'b0) {
    raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
  }
} else if (mode() == PrivilegeMode::U) {
  if (CSR[misa].S == 1'b1) {
    if ((CSR[mcounteren].TM & CSR[scounteren].TM) == 1'b0) {
      raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
    }
  } else if (CSR[mcounteren].TM == 1'b0) {
    raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
  }
} else if (mode() == PrivilegeMode::VS) {
  if (CSR[hcounteren].TM == 1'b0 && CSR[mcounteren] == 1'b1) {
    raise(ExceptionCode::VirtualInstruction, mode(), $encoding);
  } else if (CSR[mcounteren].TM == 1'b0) {
    raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
  }
} else if (mode() == PrivilegeMode::VU) {
  if (CSR[hcounteren].TM & CSR[scounteren].TM) == 1'b0) && (CSR[mcounteren].IR == 1'b1 {
    raise(ExceptionCode::VirtualInstruction, mode(), $encoding);
  } else if (CSR[mcounteren].TM == 1'b0) {
    raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
  }
}
return read_mtime();