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CSR Bit Fields

RISC-V cycleh CSR Register

Address 0xC80Privilege UserAccess RO / RV32 high-half / 32-bitUser counters and performance-monitoring CSRs

cycleh is the RV32 high-half CSR for the user cycle counter.

Related Search Terms
cycleh CSRcycleh 0xC80RV32 cycle highRDCYCLE high half64-bit cycle readuser cycleh CSR
Bit Overview
bit 3 = only bit 3; bits 12..11 = bits 12 down to 11
MSBLSB
Field Map

Understand cycleh By Bit Fields

0 key fields
Official Basis & Search Notes

cycleh is the RV32 user-level read-only high-half counter CSR at 0xC80, used with cycle for wider cycle-count reads.

cycleh address, lowest access privilege, and access class are checked against the official CSR table: 0xC80, User, RO.
cycleh is for reading the high half of cycle on RV32; RV64 does not need this high-half CSR.
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 ManualRISC-V Unprivileged ISA Manual

What To Check First When Reading This CSR

  • - First confirm that the current hart implements cycleh; Instructions accessing nonexistent CSRs are reserved; exceptions for implemented CSR accesses still follow the applicable privilege, virtualization, and CSR-specific rules.
  • - Use address 0xC80 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

  • - cycleh is a read-only CSR; an attempted write raises an illegal-instruction exception.

Put It Back Into A Real Flow

1

Read cycleh to obtain hardware or runtime state.

2

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

3

If a read is blocked, handle the applicable illegal-instruction or virtual-instruction exception path.

FAQ

Can cycleh 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 cycleh as User. Instructions accessing nonexistent CSRs are reserved; exceptions for implemented CSR accesses still follow the applicable privilege, virtualization, and CSR-specific rules.

What is easiest to miss when using cycleh?

cycleh 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.