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[/] [zipcpu/] [trunk/] [rtl/] [core/] [cpuops.v] - Blame information for rev 3

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1 2 dgisselq
///////////////////////////////////////////////////////////////////////////
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//
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// Filename:    cpuops.v
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//
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// Project:     Zip CPU -- a small, lightweight, RISC CPU soft core
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//
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// Purpose:     
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//
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// Creator:     Dan Gisselquist, Ph.D.
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//              Gisselquist Tecnology, LLC
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//
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///////////////////////////////////////////////////////////////////////////
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//
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// Copyright (C) 2015, Gisselquist Technology, LLC
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//
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// This program is free software (firmware): you can redistribute it and/or
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// modify it under the terms of  the GNU General Public License as published
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// by the Free Software Foundation, either version 3 of the License, or (at
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// your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
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// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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// for more details.
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//
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// License:     GPL, v3, as defined and found on www.gnu.org,
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//              http://www.gnu.org/licenses/gpl.html
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//
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//
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///////////////////////////////////////////////////////////////////////////
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//
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module  cpuops(i_clk, i_rst, i_ce, i_valid, i_op, i_a, i_b, o_c, o_f, o_valid);
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        input           i_clk, i_rst, i_ce;
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        input           [3:0]    i_op;
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        input           [31:0]   i_a, i_b;
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        input                   i_valid;
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        output  reg     [31:0]   o_c;
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        output  wire    [3:0]    o_f;
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        output  reg             o_valid;
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        wire    [63:0]   w_rol_tmp;
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        assign  w_rol_tmp = { i_a, i_a } << i_b[4:0];
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        wire    [31:0]   w_rol_result;
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        assign  w_rol_result = w_rol_tmp[63:32]; // Won't set flags
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        wire    z, n, v;
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        reg     c, pre_sign, set_ovfl;
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        always @(posedge i_clk)
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                if (i_ce)
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                        set_ovfl =((((i_op==4'h0)||(i_op==4'h8)) // SUB&CMP
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                                                &&(i_a[31] != i_b[31]))
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                                ||((i_op==4'ha)&&(i_a[31] == i_b[31])) // ADD
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                                ||(i_op == 4'hd) // LSL
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                                ||(i_op == 4'hf)); // LSR
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        always @(posedge i_clk)
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                if (i_ce)
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                begin
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                        pre_sign <= (i_a[31]);
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                        c <= 1'b0;
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                        casez(i_op)
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                        4'b?000:{c,o_c } <= {(i_b>i_a),i_a - i_b};// CMP/SUB
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                        4'b?001:   o_c   <= i_a & i_b;          // BTST/And
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                        // 4'h4:   o_c   <= i_a[15:0] * i_b[15:0];
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                        4'h5:      o_c   <= w_rol_result;       // ROL
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                        4'h6:      o_c   <= { i_a[31:16], i_b[15:0] }; // LODILO
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                        4'h7:      o_c   <= { i_b[15:0], i_a[15:0] }; // LODIHI
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                        4'ha: { c, o_c } <= i_a + i_b;          // Add
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                        4'hb:      o_c   <= i_a | i_b;          // Or
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                        4'hc:      o_c   <= i_a ^ i_b;          // Xor
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                        4'hd: { c, o_c } <= {1'b0, i_a } << i_b[4:0];    // LSL
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                        4'he: { c, o_c } <= { i_a[31],i_a}>> (i_b[4:0]);// ASR
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                        4'hf: { c, o_c } <= { 1'b0, i_a } >> (i_b[4:0]);// LSR
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                        default:   o_c   <=       i_b;          // MOV, LDI
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                        endcase
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                end
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        assign  z = (o_c == 32'h0000);
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        assign  n = (o_c[31]);
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        assign  v = (set_ovfl)&&(pre_sign != o_c[31]);
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        assign  o_f = { v, n, c, z };
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        initial o_valid = 1'b0;
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        always @(posedge i_clk)
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                if (i_rst)
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                        o_valid <= 1'b0;
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                else if (i_ce)
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                        o_valid <= i_valid;
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                else if (~i_ce)
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                        o_valid <= 1'b0;
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endmodule

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