RISC-V instreth CSR Register

Address 0xC82Privilege UserAccess RO / RV32 high-half / 32-bitUser counters and performance-monitoring CSRs

instreth is the RV32 high-half CSR for the user instructions-retired counter.

Related Search Terms

instreth CSR instreth 0xC82 RV32 instret high RDINSTRET high half 64-bit instret read user instreth CSR

Bit Overview

Hover for details · Click to jump↗Open Official Manual

bit 3 = only bit 3; bits 12..11 = bits 12 down to 11

MSBLSB

Reserved63:32VALUE31:0RO

Field Map

Understand instreth By Bit Fields

1 key fields

31:0

VALUE

Full register value of instreth; bits not split out here follow the relevant extension or privileged specification, and reserved or WPRI fields should be preserved when writing other fields and ignored on reads.

VALUE (bits 31:0) — Full register value of instreth; bits not split out here follow the relevant extension or privileged specification, and reserved or WPRI fields should be preserved when writing other fields and ignored on reads.

What This Field Controls

- Full register value of instreth; bits not split out here follow the relevant extension or privileged specification, and reserved or WPRI fields should be preserved when writing other fields and ignored on reads.

Common Values

This field is better understood together with surrounding context than as a fixed memorized enumeration.

↗Open Official Manual

Official Basis & Search Notes

instreth is the RV32 user-level read-only high-half counter CSR at 0xC82, used with instret for wider retired-instruction counts.

instreth address, lowest access privilege, and access class are checked against the official CSR table: 0xC82, User, RO.

instreth is for reading the high half of instret on RV32; it represents the upper retired-instruction count bits.

This is a read-only CSR; do not write it. Ignore reserved or WPRI field values on reads, and preserve those fields when writing other writable fields in the same CSR.

RISC-V Privileged Architecture Manual RISC-V Unprivileged ISA Manual

What To Check First When Reading This CSR

- First confirm that the current hart implements instreth; unimplemented or insufficiently privileged accesses raise an illegal-instruction exception.
- Use address 0xC82 and the lowest access privilege (User) to decide whether software may read it directly.
- Do not assume fixed values for reserved, WARL, or WLRL bits; interpret the value according to the specification and implementation.

Risk Checks Before Writing

- instreth is a read-only CSR; writes raise an illegal-instruction exception or are disallowed by the implementation.

Put It Back Into A Real Flow

Read instreth to obtain hardware or runtime state.

Interpret the returned value according to the field descriptions and do not attempt to write it back.

If reading fails at the current privilege level, handle the illegal-instruction exception path.

FAQ

Can instreth be accessed from any privilege level?

Do not decide from the CSR name alone. The official CSR address encoding and tables define the lowest access privilege; this entry records instreth as User. Access with insufficient privilege or to an unimplemented CSR raises an illegal-instruction exception.

What is easiest to miss when using instreth?

instreth is read-only. Treat it as an observation point, do not try to write it, and do not depend on fixed values for reserved or WPRI fields.