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package ISA is
type Byte is mod 2 ** 8;
type Address is mod 2 ** 12;
type Register_Index is mod 2 ** 4;
type Bank is array (Address) of Byte;
type Register_Bank is array (Register_Index) of Byte;
type Pixel is array (0 .. Byte'Size - 1) of Boolean;
pragma Pack (Pixel);
type Opcode_Value is mod 2 ** 12;
type Opcode_Raw is mod 2 ** 16;
type Opcode_Class is (
Flow, Jump, Call, Equal, Not_Equal, Compare, Set_Register, Add, Math,
Not_Compare, Set_Address, Jump_Relative, Random, Draw_Sprite, Input, Misc
) with Size => 4;
type Opcode is record
Value : Opcode_Value;
Class : Opcode_Class;
end record with
Size => Opcode_Raw'Size;
for Opcode use record
Value at 0 range 0 .. 11;
Class at 0 range 12 .. 15;
end record;
for Opcode_Class use (
Flow => 0,
Jump => 1,
Call => 2,
Equal => 3,
Not_Equal => 4,
Compare => 5,
Set_Register => 6,
Add => 7,
Math => 8,
Not_Compare => 9,
Set_Address => 10,
Jump_Relative => 11,
Random => 12,
Draw_Sprite => 13,
Input => 14,
Misc => 15);
Start_Address : constant Address := 16#200#;
function To_Byte (O : Opcode) return Byte;
function X_Register (O : Opcode) return Register_Index;
function Y_Register (O : Opcode) return Register_Index;
end ISA;
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