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Use register_lookup to answer what a register means. Use GDB to answer what value the target holds. Keeping those steps separate prevents a reset value from being reported as a live measurement.

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Load SVD data

Embedder loads SVD-derived device data for the project’s selected platform. It checks the local .embedder/svd-cache first, then fetches project SVD data when the platform provides it. The register tool is available only when at least one valid device is loaded. Refresh the project metadata if register_lookup reports:
When several devices are loaded, results include a device tag. State which MCU or core you intend to inspect.

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Browse a peripheral

Ask for a peripheral name to list its registers:
The result includes:
  • Peripheral base address
  • Register address, width, and access type
  • Register and field descriptions when present
  • Bit ranges when you request fields
Peripheral and register names are matched case-insensitively. If an exact name fails, Embedder can suggest a close SVD name.

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Inspect one register

Give both the peripheral and register:
An SVD register can define these access rules:
  • read-only
  • write-only
  • read-write
  • writeOnce
  • read-writeOnce
Do not write a register until you have checked its register-level and field-level access information. A read-modify-write can be unsafe on write-one-to-clear or side-effect fields even when the containing register is marked read-write; rely on the device reference when the SVD lacks that detail.

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Search by purpose

Use a free-text query when you do not know the peripheral name:
Search matches register names and descriptions, then falls back to fuzzy matching. It returns at most 50 results. When five or fewer registers match, the result includes detailed fields unless you disable them. Repeat the lookup with an exact peripheral and register before you read hardware.

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Read the live value

1

Resolve the definition

Look up the register in the SVD and record the device, absolute address, width, access type, and field layout.
2

Preserve the target when needed

Ask for an attach-only GDB session if programming or reset would destroy the state you are investigating.
3

Read the value

Use a structured GDB expression or a raw memory read with the SVD width.
4

Decode supported fields

Apply only the masks, shifts, enum values, and access semantics present in the selected SVD or device reference.
Reading a peripheral register can have side effects on some MCUs. If the reference marks a register read-to-clear, ask before reading it or use a captured copy maintained by firmware.

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Compare several cores or devices

When a project loads more than one SVD, the same peripheral name may exist in several address spaces. Ask for the device explicitly:
Do not combine a base address from one SVD with fields from another.

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Check register accesses in code

When SVD data is loaded, file-write validation can inspect changed C, Rust, and Python register accesses. It reports:
  • A write to a read-only register
  • A read from a write-only register
  • An unknown peripheral or register
  • A literal address that does not map to a known register
These diagnostics check SVD consistency. They do not prove that an access is synchronized, clocked, or safe for the current power state.

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Fix lookup problems

Confirm the project platform and MCU selection. Reopen or refresh the project so Embedder can load its cached or remote SVD data.
Search by function or accept the fuzzy suggestion, then verify the suggested peripheral against the selected device.
Check the SVD device name and silicon revision. Stop before reading or writing when the selected SVD does not match the target.
Reset values describe the SVD’s reset state. Clock, boot ROM, firmware, and debugger actions may have changed the live register before you read it.
Do not invent a mask. Use the device reference or another authoritative SVD for the exact target revision.

GDB debugging

Read the live register after you resolve its definition.

Combined workflows

Compare register evidence with logs and waveforms.
Last modified on August 24, 2026