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[/] [rtf8088/] [trunk/] [rtl/] [verilog/] [FETCH_IMMEDIATE.v] - Blame information for rev 6

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Line No. Rev Author Line
1 2 robfinch
// ============================================================================
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//  FETCH_IMM16
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//  - fetch 16 bit immediate from instruction stream as operand 'B'
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//  FETCH_IMM8
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//  - Fetch 8 bit immediate as operand 'B'
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//
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//
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//  2009-2012  Robert Finch
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//  robfinch[remove]@opencores.org
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//  Stratford
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//
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// This source file is free software: you can redistribute it and/or modify 
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// it under the terms of the GNU Lesser General Public License as published 
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// by the Free Software Foundation, either version 3 of the License, or     
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// (at your option) any later version.                                      
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//                                                                          
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// This source file is distributed in the hope that it will be useful,      
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// but WITHOUT ANY WARRANTY; without even the implied warranty of           
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            
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// GNU General Public License for more details.                             
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//                                                                          
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// You should have received a copy of the GNU General Public License        
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// along with this program.  If not, see <http://www.gnu.org/licenses/>.    
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//
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//
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//  Verilog 
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//
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// - bus is locked if immediate value is unaligned in memory
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// - immediate values are the last operand to be fetched, hence
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//   the state machine can transition into the EXECUTE state.
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// - we also know the immediate value can't be the target of an
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//   operation.
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// ============================================================================
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//
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FETCH_IMM8:
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        begin
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                `INITIATE_CODE_READ
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                state <= FETCH_IMM8_ACK;
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        end
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FETCH_IMM8_ACK:
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        if (ack_i) begin
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                `TERMINATE_CODE_READ
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                lock_o <= bus_locked;
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                b <= {{8{dat_i[7]}},dat_i};
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                state <= EXECUTE;
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        end
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FETCH_IMM16:
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        begin
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                lock_o <= 1'b1;
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                `INITIATE_CODE_READ
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                state <= FETCH_IMM16_ACK;
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        end
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FETCH_IMM16_ACK:
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        if (ack_i) begin
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                `PAUSE_CODE_READ
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                state <= FETCH_IMM16a;
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                b[ 7:0] <= dat_i;
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        end
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FETCH_IMM16a:
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        begin
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                `CONTINUE_CODE_READ
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                state <= FETCH_IMM16a_ACK;
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        end
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FETCH_IMM16a_ACK:
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        if (ack_i) begin
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                `TERMINATE_CODE_READ
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                lock_o <= bus_locked;
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                b[15:8] <= dat_i;
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                $display("Fetched #%h", {dat_i,b[7:0]});
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                state <= EXECUTE;
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        end
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