Subversion Repositories hpdmc

/*

 * Milkymist VJ SoC

 * Copyright (C) 2007, 2008, 2009 Sebastien Bourdeauducq

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, version 3 of the License.

 *

 * This program 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/>.

 */

module hpdmc_banktimer(

        input sys_clk,

        input sdram_rst,

        input tim_cas,

        input [1:0] tim_wr,

        input read,

        input write,

        output reg precharge_safe

);

reg [2:0] counter;

always @(posedge sys_clk) begin

        if(sdram_rst) begin

                counter <= 3'd0;

                precharge_safe <= 1'b1;

        end else begin

                if(read) begin

                        /* see p.26 of datasheet :

                         * "A Read burst may be followed by, or truncated with, a Precharge command

                         * to the same bank. The Precharge command should be issued x cycles after

                         * the Read command, where x equals the number of desired data element

                         * pairs"

                         */

                        counter <= 3'd4;

                        precharge_safe <= 1'b0;

                end else if(write) begin

                        counter <= {1'b1, tim_wr};

                        precharge_safe <= 1'b0;

                end else begin

                        if(counter == 3'b1)

                                precharge_safe <= 1'b1;

                        if(~precharge_safe)

                                counter <= counter - 3'b1;

                end

        end

end

endmodule