Register Field Access Notation

The register tables in this manual are generated from each block’s SystemRDL description by the PeakRDL toolchain. Their Access column reports a field’s software access together with any read or write side effect as one compact token, so a status bit that a write of 1 clears reads as RW1C rather than a bare RW. This appendix decodes that notation.

An Access cell is built in three parts:

  1. a base access token, giving whether software can read the field, write it, or neither;

  2. an optional write side-effect suffix joined directly to the base for an effect that an individual written bit triggers (RW1C, W1S, RW0C);

  3. optional space-separated flags for whole-field write effects, read effects, and single-cycle pulses (R RC, RW WS, W 1P).

A field with no side effect keeps the bare base token. The same base tokens appear in the per-register summary tables, where they aggregate the access of the register’s fields.

Table 1. Register field access tokens
Token Meaning SystemRDL property

Base access

R

Software can read the field.

sw = r

W

Software can write the field.

sw = w

RW

Software can read and write the field.

sw = rw

-

Reserved, or no software access.

sw = na, or a reserved gap

Write side-effect suffix — acts on the individual written bit

1C

Writing 1 to a bit clears it; writing 0 leaves it.

onwrite = woclr

1S

Writing 1 to a bit sets it.

onwrite = woset

1T

Writing 1 to a bit toggles it.

onwrite = wot

0C

Writing 0 to a bit clears it.

onwrite = wzc

0S

Writing 0 to a bit sets it.

onwrite = wzs

0T

Writing 0 to a bit toggles it.

onwrite = wzt

Write flags — act on any write to the field

WC

Any write clears the whole field.

onwrite = wclr

WS

Any write sets the whole field.

onwrite = wset

WMOD

A write invokes a block-specific hardware function.

onwrite = wuser

Read flags

RC

Reading the field clears it.

onread = rclr

RS

Reading the field sets it.

onread = rset

RMOD

Reading the field invokes a block-specific hardware function.

onread = ruser

Pulse

1P

The field self-clears the cycle after it is written, producing a one-cycle pulse.

singlepulse

1. References

Table 1 follows the field-property semantics of the SystemRDL 2.0 register description language (Accellera), as rendered by the PeakRDL toolchain.

  • PeakRDL — the control and status register generator toolchain that produces these register tables.

  • systemrdl-compiler field properties — the onwrite, onread and singlepulse properties and their woclr / woset / rclr / rset shorthand forms.