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// ============================================================================

//  FETCH_IMM16

//  - fetch 16 bit immediate from instruction stream as operand 'B'

//  FETCH_IMM8

//  - Fetch 8 bit immediate as operand 'B'

//

//

//  2009-2012  Robert Finch

//  robfinch[remove]@finitron.ca

//  Stratford

//

// This source file is free software: you can redistribute it and/or modify 

// it under the terms of the GNU Lesser General Public License as published 

// by the Free Software Foundation, either version 3 of the License, or     

// (at your option) any later version.                                      

//                                                                          

// This source file is distributed in the hope that it will be useful,      

// but WITHOUT ANY WARRANTY; without even the implied warranty of           

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            

// GNU General Public License for more details.                             

//                                                                          

// You should have received a copy of the GNU General Public License        

// along with this program.  If not, see <http://www.gnu.org/licenses/>.    

//

//

//  Verilog 

//

// - bus is locked if immediate value is unaligned in memory

// - immediate values are the last operand to be fetched, hence

//   the state machine can transition into the EXECUTE state.

// - we also know the immediate value can't be the target of an

//   operation.

// ============================================================================

//

FETCH_IMM8:

        begin

                code_read();

                state <= FETCH_IMM8_ACK;

        end

FETCH_IMM8_ACK:

        if (ack_i) begin

                term_code_read();

                lock_o <= bus_locked;

                b <= {{8{dat_i[7]}},dat_i};

                state <= EXECUTE;

        end

FETCH_IMM16:

        begin

                lock_o <= 1'b1;

                code_read();

                state <= FETCH_IMM16_ACK;

        end

FETCH_IMM16_ACK:

        if (ack_i) begin

                pause_code_read();

                state <= FETCH_IMM16a;

                b[ 7:0] <= dat_i;

        end

FETCH_IMM16a:

        begin

                continue_code_read();

                state <= FETCH_IMM16a_ACK;

        end

FETCH_IMM16a_ACK:

        if (ack_i) begin

                term_code_read();

                lock_o <= bus_locked;

                b[15:8] <= dat_i;

                $display("Fetched #%h", {dat_i,b[7:0]});

                state <= EXECUTE;

        end