`define load_inst		4'd0
`define store_inst		4'd1
`define alu_inst		4'd2
`define control_transfer_inst	4'd3

`define ACCn		2'd0
`define Xn		2'd1
`define Sn		2'd2
`define PCn		2'd3

`define Never		4'd0
`define Always		4'd1
`define Zequal0		4'd2
`define Zequal1		4'd3

`define justA		4'd0
`define notA		4'd1
`define lslA		4'd2
`define lsrA		4'd3
`define AaddB		4'd4
`define AsubB		4'd5
`define AandB		4'd6
`define AorB		4'd7
`define justB		4'd8






`define NOP		{`load_inst,`ACCn,`ACCn,`justA}
`define LDA		{`load_inst,`ACCn,`ACCn,`justB}
`define LDX		{`load_inst,`ACCn,`Xn,`justB}
`define LDS		{`load_inst,`ACCn,`Sn,`justB}
`define STA		{`store_inst,`ACCn,`ACCn,`justA}
`define STX		{`store_inst,`Xn,`Xn,`justA}
`define STS		{`store_inst,`Sn,`Sn,`justA}
`define ADD		{`alu_inst,`ACCn,`ACCn,`AaddB}
`define SUB		{`alu_inst,`ACCn,`ACCn,`AsubB}
`define AND		{`alu_inst,`ACCn,`ACCn,`AandB}
`define OR		{`alu_inst,`ACCn,`ACCn,`AorB}
`define COM		{`alu_inst,`ACCn,`ACCn,`notA}
`define LSL		{`alu_inst,`ACCn,`ACCn,`lslA}
`define LSR		{`alu_inst,`ACCn,`ACCn,`lsrA}
`define BA		{`control_transfer_inst,`PCn,`PCn,`Always}
`define BEQ		{`control_transfer_inst,`PCn,`PCn,`Zequal1}
`define BNE		{`control_transfer_inst,`PCn,`PCn,`Zequal0}

`define INHERENT	4'd0
`define PC_RELATIVE	4'd1
`define IMMEDIATE	4'd2
`define DIRECT		4'd3
`define INDEXED		4'd4