RISC-V sireg6 CSR Register

Address 0x157Privilege SupervisorAccess RW / XLENSupervisor AIA, timer, and indirect interrupt CSRs

sireg6 (0x157) is an Sscsrind Supervisor indirect-register alias 6 that accesses extension state selected by siselect.

Related Search Terms

sireg6 CSR sireg6 0x157 sireg alias siselect CSR Sscsrind indirect CSR

Bit Overview

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

MSBLSB

ALIAS_DATA63:0Depends on select

Field Map

Understand sireg6 By Bit Fields

1 key fields

XLEN-1:0

ALIAS_DATA

Depends on select

Alias data window whose semantics are defined by the extension selected by siselect. Accessing sireg6 in the delegated-counter 0x40..0x5F range raises an illegal-instruction exception; in the CTR 0x200..0x2FF range sireg6 is read-only zero; in AIA 0x30..0x3F and 0x70..0xFF ranges accesses to sireg2..sireg6 raise illegal-instruction exceptions.

ALIAS_DATA (bits XLEN-1:0) — Alias data window whose semantics are defined by the extension selected by siselect. Accessing sireg6 in the delegated-counter 0x40..0x5F range raises an illegal-instruction exception; in the CTR 0x200..0x2FF range sireg6 is read-only zero; in AIA 0x30..0x3F and 0x70..0xFF ranges accesses to sireg2..sireg6 raise illegal-instruction exceptions.

What This Field Controls

- Alias data window whose semantics are defined by the extension selected by siselect. Accessing sireg6 in the delegated-counter 0x40..0x5F range raises an illegal-instruction exception; in the CTR 0x200..0x2FF range sireg6 is read-only zero; in AIA 0x30..0x3F and 0x70..0xFF ranges accesses to sireg2..sireg6 raise illegal-instruction exceptions.

Common Values

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

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Official Basis & Search Notes

sireg6 is not an independent fixed-meaning register; it is an alias window selected by siselect.

Sscsrind defines sireg* behavior through the siselect/sireg* combination and the selected extension.

CTR uses siselect 0x200..0x2FF for CTR entries, where sireg6 is read-only zero; sireg6 raises an illegal-instruction exception in delegated-counter 0x40..0x5F ranges.

AIA 0x30..0x3F and 0x70..0xFF ranges are accessed through sireg only; accesses to sireg2..sireg6 raise illegal-instruction exceptions.

Do not assume zero reads, writability, or fixed side effects for unimplemented select values.

RISC-V Privileged Architecture Manual - CSR table RISC-V Privileged Architecture Manual - Smcsrind/Sscsrind RISC-V Advanced Interrupt Architecture - IMSIC CSRs RISC-V Privileged Architecture Manual - Smctr RISC-V Privileged Architecture Manual

What To Check First When Reading This CSR

- First confirm that the hart implements Sscsrind and that Smstateen has not blocked the current access through mstateen0.CSRIND or hstateen0.CSRIND.
- Use address 0x157, the lowest access privilege, and the official access class to decide whether software may access it directly.
- Do not assume fixed values for reserved, WPRI, WARL, or WLRL fields; interpret them according to the specification and implementation.

Risk Checks Before Writing

- When writing sireg6, modify only the officially defined target fields and preserve unchanged bits.
- Handle WARL, WLRL, WPRI, and reserved fields according to the official specification; do not overwrite the whole CSR as an ordinary integer.

Put It Back Into A Real Flow

First write siselect to choose the indirect-register number.

Then use the selected extension definition to decide whether sireg6 accesses state, reads as zero, or raises an illegal-instruction exception.

Do not use sireg6 for AIA iprio or IMSIC interrupt-file ranges; those AIA ranges use sireg only, and accesses to sireg2..sireg6 raise illegal-instruction exceptions.

FAQ

Why are sireg6 bit fields unlike ordinary CSRs?

Because it is an alias window; bit fields depend on the current siselect value and selected extension.