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[/] [xulalx25soc/] [trunk/] [rtl/] [wbuidleint.v] - Rev 21
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//////////////////////////////////////////////////////////////////////////////// // // Filename: wbuidleint.v // // Project: XuLA2 board // // Purpose: Creates an output for the interface, inserting idle words and // words indicating an interrupt has taken place into the output // stream. Henceforth, the output means more than just bus transaction // results. It may mean there is no bus transaction result to report, // or that an interrupt has taken place. // // // Creator: Dan Gisselquist, Ph.D. // Gisselquist Technology, LLC // //////////////////////////////////////////////////////////////////////////////// // // Copyright (C) 2015, Gisselquist Technology, LLC // // This program is free software (firmware): you can redistribute it and/or // modify it under the terms of the GNU General Public License as published // by the Free Software Foundation, either version 3 of the License, or (at // your option) any later version. // // This program is distributed in the hope that it will be useful, but WITHOUT // ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or // FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License // for more details. // // License: GPL, v3, as defined and found on www.gnu.org, // http://www.gnu.org/licenses/gpl.html // // //////////////////////////////////////////////////////////////////////////////// // // module wbuidleint(i_clk, i_stb, i_codword, i_cyc, i_busy, i_int, o_stb, o_codword, o_busy, i_tx_busy); input i_clk; // From the FIFO following the bus executor input i_stb; input [35:0] i_codword; // From the rest of the board input i_cyc, i_busy, i_int; // To the next stage output reg o_stb; output reg [35:0] o_codword; output reg o_busy; // Is the next stage busy? input i_tx_busy; reg int_request, int_sent; initial int_request = 1'b0; always @(posedge i_clk) if((o_stb)&&(~i_tx_busy)&&(o_codword[35:30]==6'h4)) int_request <= i_int; else int_request <= (int_request)||(i_int); // Now, for the idle counter wire idle_expired; reg idle_state; reg [35:0] idle_counter; initial idle_counter = 36'h0000; always @(posedge i_clk) if ((i_stb)||(o_stb)) idle_counter <= 36'h000; else if (~idle_counter[35]) idle_counter <= idle_counter + 36'd43; initial idle_state = 1'b0; always @(posedge i_clk) if ((o_stb)&&(~i_tx_busy)&&(o_codword[35:31]==5'h0)) idle_state <= 1'b1; else if (~idle_counter[35]) idle_state <= 1'b0; assign idle_expired = (~idle_state)&&(idle_counter[35]); initial o_stb = 1'b0; initial o_busy = 1'b0; always @(posedge i_clk) if ((o_stb)&&(i_tx_busy)) begin o_busy <= 1'b1; end else if (o_stb) // and not i_tx_busy begin // Idle one clock before becoming not busy o_stb <= 1'b0; o_busy <= 1'b1; end else if (o_busy) o_busy <= 1'b0; else if (i_stb) // and (~o_busy)&&(~o_stb) begin // On a valid output, just send it out // We'll open this strobe, even if the transmitter // is busy, just 'cause we might otherwise lose it o_codword <= i_codword; o_stb <= 1'b1; o_busy <= 1'b1; end else if ((int_request)&&(~int_sent)) begin o_stb <= 1'b1; o_codword <= { 6'h4, 30'h0000 }; // interrupt codeword o_busy <= 1'b1; end else if (idle_expired) begin // Strobe, if we're not writing or our // last command wasn't an idle o_stb <= 1'b1; o_busy <= 1'b1; if (i_cyc) o_codword <= { 6'h1, 30'h0000 }; // idle codeword, bus busy else o_codword <= { 6'h0, 30'h0000 }; end initial int_sent = 1'b0; always @(posedge i_clk) if ((int_request)&&((~o_stb)&&(~o_busy)&&(~i_stb))) int_sent <= 1'b1; else if (~i_int) int_sent <= 1'b0; endmodule
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