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# A basic graphics processor

The processor only knows how to render a list of sprites which have a velocity.

## Problems encountered

- GHDL does not support external signals (https://github.com/ghdl/ghdl/issues/24). Workaround:
  - [using global signals](https://stackoverflow.com/questions/40286725/how-can-i-get-internal-signals-to-testbench-in-vhdl-97-and-isim/40313051#40313051)

## Potential questions

- In a testbench you want to wait for a signal to be activated in a non-sensitivized process with `wait for` statements. What could be the problem with the following?

  ```vhdl
  wait for tlast = '1';
  ```
  You have to add `wait on tlast for tlast = '1'`
  <!--TODO I have to verify this in another simulator -->

- what happens if we do this after directly after reset:

  ```
  for line in frame'range loop
  	for pixel in line'range loop
  		pixel <= '0';
  	end loop;
  end loop;
  ```

## Handy resources

- https://www.synthworks.com/downloads/type_pkg_quickref.pdf