muxing

extras/muxing.vhdl

extras_2008/muxing_2008.vhdl

Dependencies

common_2008 (for muxing_2008)

Description

A set of routines for creating parameterized multiplexers, decoders, and demultiplexers. The VHDL-2008 version has an additional mux() function that can select from multi-bit inputs implemented in VHDL-2008 syntax.

Example usage

signal sel : unsigned(3 downto 0);
signal d, data : std_ulogic_vector(0 to 2**sel'length-1);
signal d2  : std_ulogic_vector(0 to 10);
signal m   : std_ulogic;
...
d <= decode(sel);             -- Full binary decode
d2 <= decode(sel, d2'length); -- Partial decode

m <= mux(data, sel);          -- Mux with internal decoder
m <= mux(data, d);            -- Mux with external decoder

d2 <= demux(m, sel, d2'length);

Muxing vectors with VHDL-2008:

library extras_2008;
use extras_2008.muxing.all;
use extras_2008.common.sulv_array;

signal sel : unsigned(3 downto 0);
signal m : std_ulogic_vector(7 downto 0);
signal data : sulv_array(0 to 2**sel'length-1)(m'range);
...
m <= mux(data, sel);

Subprograms

muxing.decode (Sel : unsigned) → std_ulogic_vector
Decoder with variable sized output (power of 2).
Parameters:
  • Sel (unsigned) – Numeric value to decode (range 0 to 2**Sel’length-1)
Returns:

Decoded (one-hot) representation of Sel.
muxing.decode (Sel : unsigned; Size : positive) → std_ulogic_vector
Decoder with variable sized output (user specified).
Parameters:
  • Sel (unsigned) – Numeric value to decode (range 0 to Size-1)
  • Size (positive) – Number of bits in result (leftmost bits)
Returns:

Decoded (one-hot) representation of Sel.
muxing.mux (Inputs : std_ulogic_vector; Sel : unsigned) → std_ulogic
Multiplexer with variable sized inputs.
Parameters:
  • Inputs (std_ulogic_vector) – Inputs to select from
  • Sel (unsigned) – Input to select
Returns:

Selected input.
muxing.mux (Inputs : std_ulogic_vector; One_hot_sel : std_ulogic_vector) → std_ulogic
Multiplexer with variable sized inputs using external decoder.
Parameters:
  • Inputs (std_ulogic_vector) – Inputs to select from
  • One_hot_sel (std_ulogic_vector) – Input to select (generated by decode())
Returns:

Selected input.
muxing.demux (Input : std_ulogic; Sel : unsigned; Size : positive) → std_ulogic_vector
Demultiplexer with variable sized inputs.
Parameters:
  • Input (std_ulogic) – Bit to demultiplex
  • Sel (unsigned) – Position of Bit in result
  • Size (positive) – Length of the result
Returns:

Vector with selected bit connected to the Input.

VHDL-2008 variant

Subprograms

muxing.decode (Sel : unsigned) → std_ulogic_vector
Decoder with variable sized output (power of 2).
Parameters:
  • Sel (unsigned) – Numeric value to decode (range 0 to 2**Sel’length-1)
Returns:

Decoded (one-hot) representation of Sel.
muxing.decode (Sel : unsigned; Size : positive) → std_ulogic_vector
Decoder with variable sized output (user specified).
Parameters:
  • Sel (unsigned) – Numeric value to decode (range 0 to Size-1)
  • Size (positive) – Number of bits in result (leftmost bits)
Returns:

Decoded (one-hot) representation of Sel.
muxing.mux (Inputs : std_ulogic_vector; Sel : unsigned) → std_ulogic
Multiplexer with variable sized inputs.
Parameters:
  • Inputs (std_ulogic_vector) – Inputs to select from
  • Sel (unsigned) – Input to select
Returns:

Selected input.
muxing.mux (Inputs : std_ulogic_vector; One_hot_sel : std_ulogic_vector) → std_ulogic
Multiplexer with variable sized inputs using external decoder.
Parameters:
  • Inputs (std_ulogic_vector) – Inputs to select from
  • One_hot_sel (std_ulogic_vector) – Input to select (generated by decode())
Returns:

Selected input.
muxing.demux (Input : std_ulogic; Sel : unsigned; Size : positive) → std_ulogic_vector
Demultiplexer with variable sized inputs.
Parameters:
  • Input (std_ulogic) – Bit to demultiplex
  • Sel (unsigned) – Position of Bit in result
  • Size (positive) – Length of the result
Returns:

Vector with selected bit connected to the Input.
muxing.mux (Inputs : sulv_array; Sel : unsigned) → std_ulogic_vector
Multiplexer with variable sized, multi-bit inputs.
Parameters:
  • Inputs (sulv_array) – Inputs to select from
  • Sel (unsigned) – Input to select
Returns:

Selected input.