Ben Eater 6502 Kit — Day 8

It seems that the broken power supply has also destroyed the CPU itself. That's very bad and I have to order new one. Getting hold of a WDC60C02 (WDC = Western Design Center) is not that easy. It's much easier to buy a R65C02 (R = Rockwell) but the R65C02 CPU doesn't feature a fully static design which you can hardware single step. The R65C02 is also missing the WAI (Wait-for-Interrupt) and STP (Stop) instruction why rely on said fully static design of the WDC60C02.

So I'm going thought the pain of ordering a WDC60C02 from Jameco. The CPU itself is not that expensive. Sadly postage to Europe is twice the cost of the CPU. I ordered a few extras to make it worth while.

So the projects is stalled for a few weeks and I'll use the time I wait for a new CPU for some software development.

In the next step a ROM with all NOP operations will be needed. Ben Eater does this in Python but I choose to program this on my favourite language Ada. The, again over engineered, result looks like this:

with Ada.Sequential_IO;
with Ada.IO_Exceptions;
with Ada.Command_Line;
with Ada.Text_IO;
with Interfaces;

procedure Create_NOP is

  package Byte_IO is new Ada.Sequential_IO (Interfaces.Unsigned_8);

  Byte_Output : Byte_IO.File_Type;
  NOP         : constant Interfaces.Unsigned_8 := 16#EA#;
  Rom_Size    : constant                       := 32 * 2**10;

begin
  if Ada.Command_Line.Argument_Count < 1 then
     Ada.Text_IO.Put_Line ("Syntax: create_nop <output file>");
  else
     declare
        File_Name : constant String := Ada.Command_Line.Argument (1);
     begin
        Byte_IO.Create (Byte_Output, Byte_IO.Out_File, File_Name);
     exception
        when Ada.IO_Exceptions.Name_Error =>
           Ada.Text_IO.Put_Line ("File “" & File_Name & "” couldn't be created.");
           Ada.Text_IO.Put_Line ("See stack trace below for more details.");
           raise;
     end;

     for I range 1 .. Rom_Size loop
        Byte_IO.Write (Byte_Output, NOP);
     end loop;

     Byte_IO.Close (Byte_Output);
  end if;
end Create_NOP;

Yes, a little longer the Python but it has an error handler, a simple command line interpreter and outputs some help if needed.

The program uses `Sequential_IO` to write the same type of element sequentially — as the name suggest. In this case it's not just the same type of element but the very same element called `NOP` which contains an unsigned integer with the value if hex `EA`. This is done 32768 times (32×2¹⁰).

`EA` of course is the 6502 instruction for NOP (No Operation). Not a very complicated program. Here you see the ROM being written.

You find the full source code with makefiles, project files and everything on GitLab: 6502Tutorial — Tools/Create_NOP