MULTIPLEXER

Select the type of multiplexer you want: Type 1 or Type 2. Type 1 includes one input bus and one select line. Type 2 includes at least two input buses and one select line.

Figure 4.22 The Multiplexer Module

The Type 1 Multiplexer module routes one bit of an n-bit Input to the Output under the control of the Select input port, where the value of n is determined by the width of the input port. The Select input encoding can be binary or one-hot.

Figure 4.23 The Type 1 Multiplexer Logic Diagram

The Type 2 Multiplexer module routes one of two or more Input Buses to the Output Bus under the control of the Select input port. The Select input encoding can be binary or one-hot.

Figure 4.24 The Type 2 Multiplexer Module

Figure 4.25 The Type 2, 2-input Multiplexer Logic Diagram

Input Pins

M is the Mux input bus data port of the Type 1 Multiplexer. The width of this bus is specified via the Bus Width attribute.

Connections: The Mux input is always specified on Type 1 Multiplexers.

MA, MB, ..., MH are the input bus data ports of the Type 2 Multiplexer. For a 3-input bus module with binary encoded Select, MA is selected when the Select input evaluates to zero, MB is selected when the Select input evaluates to 1, and MC is selected when the Select input evaluates to 2. If the value of the Select input is 3, the Multiplexer outputs are all High.

Connections: The MA and MB inputs are always connected on Type 2 Multiplexers. The other inputs are dependent on the value of the INPUT_BUSES attribute. For example, if INPUT_BUSES=4, then MA, MB, MC, and MD would be the input buses shown. The input and output buses must have the same width. The maximum bus width is 64.

The Select input port chooses which input bus line is directed to the Multiplexer output line. Depending on the encoding scheme, the Select input can address more lines than are available on the input bus.

Connections: The Select input is required. The Select input port is from 1 to 64 bits wide on a Type 1 Multiplexer. On a Type 2 Multiplexer, the Select input port is from 1 to 8 bits wide, depending on the Select encoding method.

Output Pins

The Multiplexer output line (for a Type 1 multiplexer) or Bus port (for a Type 2 multiplexer) reflects the selected input bus port data. If the selected input port is unavailable (out-of-range), the Multiplexer outputs are High.

Connections: The output pin must be connected.

Attributes

The Operation attribute specifies the type of multiplexer module you want: single-bus input or multiple-bus input.

Usage: Valid values are Type 1 (single-bus input) and Type 2 (multiple-bus input).

Style defines the implementation style (area or speed preference).

Usage: For more information, see the “Implementation Styles” section of the “Understanding Attributes” chapter.

Use the Input Buses attribute to specify the number of input buses. The number of buses can be any number in the range from 2 to 8.

Usage: This attribute only applies to Type 2 modules.

Use the Encoding attribute to specify the encoding scheme used to represent the Select bus.

Usage: Valid values are Binary and One Hot.