Code conversion

The nmigen.lib.coding module provides building blocks for conversion between different encodings of binary numbers.

One-hot coding

class nmigen.lib.coding.Encoder

Encode one-hot to binary.

If one bit in i is asserted, n is low and o indicates the asserted bit. Otherwise, n is high and o is 0.

Parameters:

width (int) – Bit width of the input

Variables:

• i (Signal(width), in) – One-hot input.

• o (Signal(range(width)), out) – Encoded natural binary.

• n (Signal, out) – Invalid: either none or multiple input bits are asserted.

class nmigen.lib.coding.Decoder

Decode binary to one-hot.

If n is low, only the i-th bit in o is asserted. If n is high, o is 0.

Parameters:

width (int) – Bit width of the output.

Variables:

• i (Signal(range(width)), in) – Input binary.

• o (Signal(width), out) – Decoded one-hot.

• n (Signal, in) – Invalid, no output bits are to be asserted.

Priority coding

class nmigen.lib.coding.PriorityEncoder

Priority encode requests to binary.

If any bit in i is asserted, n is low and o indicates the least significant asserted bit. Otherwise, n is high and o is 0.

Parameters:

width (int) – Bit width of the input.

Variables:

• i (Signal(width), in) – Input requests.

• o (Signal(range(width)), out) – Encoded natural binary.

• n (Signal, out) – Invalid: no input bits are asserted.

class nmigen.lib.coding.PriorityDecoder

Decode binary to priority request.

Identical to Decoder.

Gray coding

class nmigen.lib.coding.GrayEncoder

Encode binary to Gray code.

Parameters:

width (int) – Bit width.

Variables:

• i (Signal(width), in) – Natural binary input.

• o (Signal(width), out) – Encoded Gray code.

class nmigen.lib.coding.GrayDecoder

Decode Gray code to binary.

Parameters:

width (int) – Bit width.

Variables:

• i (Signal(width), in) – Gray code input.

• o (Signal(width), out) – Decoded natural binary.