time
Timer for RDTIME Instruction
| This CSR does not exist, and access will cause an IllegalInstruction exception. |
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Shadow of the memory-mapped M-mode CSR Privilege mode access is controlled with mcounteren.TM, scounteren.TM, and hcounteren.TM as follows:
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Software read
This CSR may return a value that is different from what is stored in hardware.
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();