hp-saturn/opcodes/z_alu_phase_2.v

`include "decstates.v"

case (decstate)
`DEC_ALU_INIT, `DEC_ALU_CONT: begin
`ifdef SIM
    if (alu_debug) begin
    	$display("----------------------- z_alu_phase_2 - Do calculations ------------------------");
        $display("data received from reading : %h", bus_nibble_out);
    end
`endif

    case (alu_op)
    `ALU_OP_ZERO: begin
        alu_res1 <= 0;
        alu_res_carry <= 0;
    end
    `ALU_OP_COPY: begin
        case (alu_reg_src1)
        `ALU_REG_A,
        `ALU_REG_B,
        `ALU_REG_C,
        `ALU_REG_D: alu_res1 <= alu_src1;
        `ALU_REG_M: alu_res1 <= bus_nibble_out;
        default: begin
            $display("ALU_P2 ERROR : ALU_OP %d REGISTER NOT IMPLEMENTED %d", alu_op, alu_reg_src1);
            alu_p2_halt <= 1;
        end
        endcase
        alu_res_carry <= 0;
    end
    `ALU_OP_2CMPL: begin
        {alu_res_carry, alu_res1} <= !alu_src1 + alu_carry;
    end
   `ALU_OP_1CMPL: begin
        alu_res1 <= ~alu_src1;
        alu_res_carry <= 0;
    end
    `ALU_OP_INC: begin
        {alu_res_carry, alu_res1} <= alu_src1 + alu_carry;
    end
    `ALU_OP_TEST_EQ: begin
        alu_res_carry <= (alu_src1 == alu_src2) & alu_carry;
    end
    `ALU_OP_TEST_NEQ: begin
        alu_res_carry <= (alu_src1 != alu_src2) & alu_carry;
    end
    default: $display("ALU PHASE 2 ERROR : unknown op %d", alu_op);
    endcase
end
endcase