This module reads the status of the buttons on a SNES gamepad. The user interacts with the module via three signals:

* rd
* busy
* buttons

The *rd* signal is used to command the module to begin the read operation. The *busy* signal is active high when the module is executing a read. Lastly, the *buttons* signal contains the status of the SNES buttons at the completion of the read.

The module interacts with the SNES controller via three signals:

* snes_latch
* snes_clk
* snes_data

The read process is initiated by holding the *snes_latch* signal high for 12 us. At the end of the *snes_latch* signal, the first button status (B) is available on *snes_data* and the *snes_clk* cycles through sixteen rising edge transitions with a 12 us clock period. The *snes_data* signal is read on the falling edge of *snes_clk*. The *snes_data* signal is active low and the module inverts the result.