hp-saturn/opcodes/Dx_regs_field_A.v

/******************************************************************************
 * Dx
 * register manipulation field A
 *
 */ 


`include "decstates.v"

`DEC_DX: begin
    field <= `T_FIELD_A;
    alu_first <= 0;
    alu_last  <= 4;

    case (nb_in[3:2])
    2'b00: begin
        alu_op <= `ALU_OP_ZERO;
        alu_reg_dest <= {2'b00, nb_in[1:0]};
    end
    2'b01: begin
        alu_op <= `ALU_OP_COPY;
        alu_reg_dest <= {2'b00, nb_in[1:0]};
        alu_reg_src1 <= {2'b00, nb_in[0], !(nb_in[1] | nb_in[0])};
    end
    2'b10: begin
        alu_op <= `ALU_OP_COPY;
        alu_reg_dest <= {2'b00, nb_in[0], !(nb_in[1] | nb_in[0])};
        alu_reg_src1 <= {2'b00, nb_in[1:0]};
    end
    2'b11: begin
        alu_op <= `ALU_OP_EXCH;
        alu_reg_dest <= {2'b00, nb_in[1] & nb_in[0], (!nb_in[1]) & nb_in[0]};
        alu_reg_src1 <= {2'b00, nb_in[1] | nb_in[0], (!nb_in[1]) ^ nb_in[0]};
    end
    endcase
    alu_debug <= 1;
    next_cycle <= `BUSCMD_NOP;
    decstate <= `DEC_ALU_INIT;
    alu_return <= `DEC_START;
end