// internal types for eater CPU

`ifndef EATER_TYPES
`define EATER_TYPES

// CPU state (for control flags)
typedef enum logic[7:0] {
    // "regular" states
    INIT,
    PC_to_MAR,
    MEM_to_INS_PC_inc,
    // Note:
    // The Ben Eater CPU combines these steps. However.
    // I got probably a bug in my state machine,
    // or clock in the data differently,
    // but if I combine the steps, I'm trying to get
    // the instruction-dependent next state before
    // the INS is actually loaded. whoops.
    // One day later: Possible if we run the decoder on the negedge
    // PC_inc,

    // instruction dependent states

    // LDA: a) LSB of INStruction into MAR
    LDA_INS_to_MAR,
    // LDA: b) MEM -> A
    LDA_MEM_to_A,

    // ADD: a) LSB of INStruction into MAR
    ADD_INS_to_MAR,
    // ADD: b) MEM -> B
    ADD_MEM_to_B,
    // ADD: c) ALU -> A
    ADD_ALU_to_A,

    // SUB: a) LSB of INStruction into MAR
    SUB_INS_to_MAR,
    // SUB: b) MEM -> B
    SUB_MEM_to_B,
    // SUB: c) ALU -> A
    SUB_ALU_to_A,

    // STA: a) LSB of INStruction into MAR
    STA_INS_to_MAR,
    // STA: b) A -> MEM
    STA_A_to_MEM,

    // LDI: a) LSB of INStruction into A
    LDI_INS_to_A,

    // JMP: a) Put 4 LSB of INS -> PC
    JMP_INS_to_PC,
    // JMP: b) Needed??? Wait for value to be clocked in to be actually used
    // probably not needed
    JMP_NOP,

    // OUT: A -> OUT
    OUT_A_to_OUT,

    // HALT: set halt flag
    HALT_st
} CpuState;

typedef enum logic[3:0] {  
    NOP = 'b0000,
    LDA = 'b0001,
    ADD = 'b0010,
    SUB = 'b0011,
    STA = 'b0100,
    LDI = 'b0101,
    JMP = 'b0110,
    OUT = 'b1110,
    HALT_op = 'b1111
} eater_instruction;

// CPU control flags
`ifdef IVERILOG
typedef struct packed {
    logic A_out, A_in;
    logic B_out, B_in;
    logic INS_out, INS_in;
    logic MAR_in;
    logic RAM_out, RAM_in;
    logic ALU_out;
    logic PC_out, PC_in, PC_count;
    logic OUT_in;
    logic halt;
} CpuControlFlags;
`else
typedef struct {
    logic A_out, A_in;
    logic B_out, B_in;
    logic INS_out, INS_in;
    logic MAR_in;
    logic RAM_out, RAM_in;
    logic ALU_out, ALU_subtract_nadd;
    logic PC_out, PC_in, PC_count;
    logic OUT_in;
    logic halt;
} CpuControlFlags;
`endif

`endif