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[/] [klc32/] [trunk/] [rtl/] [verilog/] [POP.v] - Blame information for rev 11

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// ============================================================================
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// (C) 2011 Robert Finch
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// All Rights Reserved.
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// robfinch<remove>@opencores.org
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//
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// KLC32 - 32 bit CPU
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// POP type instructions
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// POP / UNLK
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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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//
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POP1:
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        if (ir[25:1]==25'd0)
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                state <= IFETCH;
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        else begin
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                Rn <= ir[25:21];
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                ir[25:0] <= {ir[20:1],6'b0};
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                if (ir[25:21]!=5'd0)
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                        state <= POP2;
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        end
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POP2:
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        begin
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                fc_o <= {sf,2'b01};
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                cyc_o <= 1'b1;
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                stb_o <= 1'b1;
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                sel_o <= 4'b1111;
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                adr_o <= sf ? ssp : usp;
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                state <= POP3;
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        end
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POP3:
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        if (ack_i) begin
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                cyc_o <= 1'b0;
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                stb_o <= 1'b0;
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                sel_o <= 4'b0000;
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                if (sf)
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                        ssp <= ssp + 32'd4;
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                else
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                        usp <= usp + 32'd4;
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                res <= dat_i;
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                state <= WRITEBACK;
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        end
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        else if (err_i) begin
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                cyc_o <= 1'b0;
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                stb_o <= 1'b0;
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                sel_o <= 4'b0000;
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                vector <= `BUS_ERR_VECTOR;
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                state <= TRAP;
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        end
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UNLK:
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        if (!cyc_o) begin
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                fc_o <= {sf,2'b01};
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                cyc_o <= 1'b1;
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                stb_o <= 1'b1;
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                sel_o <= 4'b1111;
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                adr_o <= a;
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                if (sf)
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                        ssp <= a;
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                else
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                        usp <= a;
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        end
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        else if (ack_i) begin
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                cyc_o <= 1'b0;
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                stb_o <= 1'b0;
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                sel_o <= 4'b0000;
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                if (sf)
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                        ssp <= ssp + 32'd4;
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                else
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                        usp <= usp + 32'd4;
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                res <= dat_i;
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                state <= WRITEBACK;
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        end
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        else if (err_i) begin
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                cyc_o <= 1'b0;
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                stb_o <= 1'b0;
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                sel_o <= 4'b0000;
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                vector <= `BUS_ERR_VECTOR;
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                state <= TRAP;
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        end
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