Memory test

[cyboman]

Hello.

I designed the memory component and then tested it. However I'm puzzled by the last three lines of the Memory.cmp file. How come the outputs are -1, -1 and 89? The addresses on those lines point to either screen memory or keyboard memory. When addresses are in the screen memory range the out value is equal to -1. I looked at the Screen chip and it only has input but no outputs, so how come the value is -1? As far as the keyboard value, I can't figure out why the value is 89? Since I get different values for the last three lines but everything else is correct, may I assume that my design is a working one?

Thank you.

[cadet1620]

The Memory.cmp file is correct. If your HDL is not passing, then it is in error.

Screen works like a RAM and for each address outputs the value that was written to that address.
See figure 5.4 for Screen.hdl.

89 is the ACSII code for "Y" which the Keyboard chip should be outputting when you hold down the "Y" at the end of the test.
See figure 5.5 for Keyboard.hdl.

--Mark

[cyboman]

Thank you for the reply. I found the problem. For some reason I didn't see the output pin of the Screen chip.