Devkit Debug Key

Hardware

The devkit "debug key" (the GB cartridge contained within the devkit) contains the following hardware:

• SIL (Silicon Labs) 2104 USB to UART bridge - Supports 300 bps to 2 mbps
• Button
• Green LED

  // Enable bus output.
  // Note: UART uses this bank.
  assign cart_tran_bank0_dir = 1'b1;

  // Enable bus input.
  assign cart_tran_bank3_dir = 1'b0;
  assign cart_tran_pin31_dir = 1'b0;

  // Pin 4 is LED.
  assign cart_tran_bank0[5]  = led;

  // Pin 6 is button, we invert since button is always high.
  assign button              = ~cart_tran_bank3[0];

  // Pin 3 is UART output
  assign cart_tran_bank0[6]  = uart_tx;

  // Pin 31 is UART input
  synch_3 rx_synch (
      cart_tran_pin31,
      uart_rx,
      clk
  );

See debug_key.v for a complete component using the debug key.

Debug key pinout image contributed by @RndMnkIII.