clean up magic numbers

src/ada_chip.adb

@@ -6,28 +6,29 @@ with Sf.Audio;
 with Sf.Audio.Sound;
 with Sf.Audio.SoundBuffer;
 
-with ISA; use ISA;
+with ISA;
 with CPU;
 with Video;
 
 procedure Ada_Chip is
    use Sf.Audio;
 
-   package Random_Byte is new Ada.Numerics.Discrete_Random (Byte);
+   package Random_Byte is new Ada.Numerics.Discrete_Random (ISA.Byte);
 
-   Steps_Per_Frame : constant := 8;
+   Steps_Per_Frame : constant := 12;
 
    State            : CPU.Instance;
    Random_Generator : Random_Byte.Generator;
-   Delay_Timer      : Byte := 0;
-   Sound_Timer      : Byte := 0;
+   Delay_Timer      : ISA.Byte := 0;
+   Sound_Timer      : ISA.Byte := 0;
 
    Beep_Sound_Buffer : constant sfSoundBuffer_Ptr :=
       SoundBuffer.createFromFile ("beep.ogg");
    Beep_Sound        : constant sfSound_Ptr := Sound.create;
 
-   procedure Draw_Sprite (VX, VY : Register_Index; N : Byte) is
+   procedure Draw_Sprite (VX, VY : ISA.Register_Index; N : ISA.Byte) is
       use Sf;
+      use ISA;
 
       X, Y       : sfUint32;
       Row        : aliased Byte;
@@ -56,13 +57,15 @@ procedure Ada_Chip is
    end Draw_Sprite;
 
    procedure Run_Step is
+      use ISA;
+
       ins : Opcode;
    begin
       ins := CPU.Get_Opcode (State);
       case ins.Class is
-         when Flow => case ins.Value is
-            when 16#E0# => Video.Clear_Screen;
-            when 16#EE# => CPU.Ret (State);
+         when Flow => case Byte (ins.Value) is
+            when ISA.Clear_Screen => Video.Clear_Screen;
+            when ISA.Ret => CPU.Ret (State);
             when others => begin
                Ada.Text_IO.Put_Line ("Unknown flow instruction!");
                Ada.Text_IO.Put_Line (Opcode_Value'Image (ins.Value));
@@ -109,13 +112,13 @@ procedure Ada_Chip is
             Draw_Sprite (X_Register (ins), Y_Register (ins),
                To_Byte (ins) mod 16);
          when Input => case To_Byte (ins) is
-            when 16#9E# =>
+            when ISA.Key_Down =>
                if Video.Key_Down
                   (Video.Key (State.Registers (X_Register (ins)) mod 16))
                then
                   CPU.Skip (State);
                end if;
-            when 16#A1# =>
+            when ISA.Key_Up =>
                if Video.Key_Up
                   (Video.Key (State.Registers (X_Register (ins)) mod 16))
                then
@@ -124,21 +127,21 @@ procedure Ada_Chip is
             when others => null;
          end case;
          when Misc => case To_Byte (ins) is
-            when 16#07# =>
+            when ISA.Get_Delay =>
                State.Registers (X_Register (ins)) := Delay_Timer;
-            when 16#0A# =>
+            when ISA.Get_Key =>
                State.Registers (X_Register (ins)) := Byte (Video.Next_Key);
-            when 16#15# =>
+            when ISA.Set_Delay =>
                Delay_Timer := State.Registers (X_Register (ins));
-            when 16#18# =>
+            when ISA.Set_Sound =>
                Sound_Timer := State.Registers (X_Register (ins));
-            when 16#1E# =>
+            when ISA.Add_Address =>
                State.Address_Register := State.Address_Register +
                   Address (State.Registers (X_Register (ins)));
-            when 16#29# =>
+            when ISA.Get_Font =>
                State.Address_Register :=
                   Address (State.Registers (X_Register (ins)) mod 16) * 5;
-            when 16#33# => begin
+            when ISA.Get_BCD => begin
                State.Memory (State.Address_Register) :=
                   State.Registers (X_Register (ins)) / 100;
                State.Memory (State.Address_Register + 1) :=
@@ -146,9 +149,9 @@ procedure Ada_Chip is
                State.Memory (State.Address_Register + 2) :=
                   State.Registers (X_Register (ins)) mod 10;
             end;
-            when 16#55# =>
+            when ISA.Reg_Store =>
                CPU.Reg_Store (State, X_Register (ins));
-            when 16#65# =>
+            when ISA.Reg_Load =>
                CPU.Reg_Load (State, X_Register (ins));
             when others => begin
                Ada.Text_IO.Put_Line ("Unknown misc instruction!");
@@ -165,6 +168,8 @@ procedure Ada_Chip is
          end;
       end case;
    end Run_Step;
+
+   use ISA;
 begin
    if Ada.Command_Line.Argument_Count /= 1 then
       Ada.Text_IO.Put_Line ("usage: adachip <.c8 file>");

src/isa.ads

@@ -42,6 +42,20 @@ package ISA is
       Input         => 14,
       Misc          => 15);
 
+   Clear_Screen : constant Byte := 16#E0#;
+   Ret          : constant Byte := 16#EE#;
+   Key_Down     : constant Byte := 16#9E#;
+   Key_Up       : constant Byte := 16#A1#;
+   Get_Delay    : constant Byte := 16#07#;
+   Get_Key      : constant Byte := 16#0A#;
+   Set_Delay    : constant Byte := 16#15#;
+   Set_Sound    : constant Byte := 16#18#;
+   Add_Address  : constant Byte := 16#1E#;
+   Get_Font     : constant Byte := 16#29#;
+   Get_BCD      : constant Byte := 16#33#;
+   Reg_Store    : constant Byte := 16#55#;
+   Reg_Load     : constant Byte := 16#65#;
+
    Start_Address : constant Address := 16#200#;
 
    function To_Byte (O : Opcode) return Byte;