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robfinch |
// ============================================================================
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// __
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// \\__/ o\ (C) 2006-2022 Robert Finch, Waterloo
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// \ __ / All rights reserved.
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// \/_// robfinch@finitron.ca
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// ||
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//
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//
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// rfTextShiftRegister.v
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// Parallel to serial data converter (shift register).
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// - shifts one or two bits at a time depending on color mode
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//
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// BSD 3-Clause License
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this
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// list of conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice,
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// this list of conditions and the following disclaimer in the documentation
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// and/or other materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//
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// ============================================================================
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//
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module rfTextShiftRegister(rst, clk, mcm, ce, ld, a, qin, d, qh);
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localparam WID=64;
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input rst; // reset
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input clk; // clock
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input mcm;
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input ce; // clock enable
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input ld; // load
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input [5:0] a; // bits 0-5 of the font width
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input qin; // serial shifting input
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input [WID-1:0] d; // data to load
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output reg [1:0] qh; // serial output
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reg [WID-1:0] q;
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always_ff @(posedge clk)
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if (rst)
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q <= {WID{1'b0}};
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else if (ce) begin
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if (ld)
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q <= d;
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else if (mcm)
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q <= {q[WID-3:0],2'b0};
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else
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q <= {q[WID-2:0],qin};
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end
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always_ff @(posedge clk)
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if (ce)
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// ToDo: fill in other sizes. However, glyph edit does not support sizes over
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// 32x32. Also we support only even widths since they may be multi-color mode.
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case(a)
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6'b011111: qh <= q[31:30];
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6'b011101: qh <= q[29:28];
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6'b011011: qh <= q[27:26];
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6'b011001: qh <= q[25:24];
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6'b010111: qh <= q[23:22];
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6'b010101: qh <= q[21:20];
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6'b010011: qh <= q[19:18];
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6'b010001: qh <= q[17:16];
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6'b001111: qh <= q[15:14];
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6'b001101: qh <= q[13:12];
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6'b001011: qh <= q[11:10];
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6'b001001: qh <= q[ 9:8];
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6'b000111: qh <= q[ 7:6];
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6'b000101: qh <= q[ 5:4];
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default: qh <= q[ 7:6];
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endcase
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endmodule
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