This example describes a two-input, 8 bit adder/subtractor design in Verilog HDL. The design unit dynamically switches between add and subtract operations with an add_sub input port.
Figure 1. Adder/Subtractor top-level diagram.
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Table 1. Adder/Subtractor Port Listing
| Port Name | Type | Description |
|---|---|---|
| dataa[7:0], datab[7:0] | Input | 8 bit data inputs |
| add_sub | Input | Input port to enable dynamic switching between add and subtract operations |
| clk | Input | Clock input |
| result[8:0] | Output | 8 bit data output and a carry/borrow most significant bit (MSB) |