# FieldDef

## class FieldDef(name: str, lsb: int, width_bits: int = 1)[source]

Bases: [`object`](https://docs.python.org/3/builtins/functions.html#object "(in Python v3.15)")

A contiguous bit field within a register (e.g. `FieldDef("mode", lsb=3, width_bits=2)` for bits [4:3]).

### name: str

### lsb: int

### width_bits: int = 1

### mask() → int[source]

Bitmask covering this field’s bits (e.g. `lsb=3, width=2` → `0b00011000`).