Subversion Repositories rtftextcontroller

// ============================================================================
//        __
//   \\__/ o\    (C) 2006-2022  Robert Finch, Waterloo
//    \  __ /    All rights reserved.
//     \/_//     robfinch<remove>@finitron.ca
//       ||
//
//
//      rfTextShiftRegister.v
//              Parallel to serial data converter (shift register).
//  - shifts one or two bits at a time depending on color mode
//
// BSD 3-Clause License
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//                                                                          
// ============================================================================
//
module rfTextShiftRegister(rst, clk, mcm, ce, ld, a, qin, d, qh);
localparam WID=64;
input rst;                      // reset
input clk;                      // clock
input mcm;
input ce;                       // clock enable
input ld;                       // load
input [5:0] a;  // bits 0-5 of the font width
input qin;                      // serial shifting input
input [WID-1:0] d;      // data to load
output reg [1:0] qh;    // serial output

reg [WID-1:0] q;

always_ff @(posedge clk)
        if (rst)
                q <= {WID{1'b0}};
        else if (ce) begin
                if (ld)
                        q <= d;
                else if (mcm)
                  q <= {q[WID-3:0],2'b0};
                else
                  q <= {q[WID-2:0],qin};
        end

always_ff @(posedge clk)
if (ce)
        // ToDo: fill in other sizes. However, glyph edit does not support sizes over
        // 32x32. Also we support only even widths since they may be multi-color mode.
        case(a)
  6'b011111:    qh <= q[31:30];
  6'b011101:    qh <= q[29:28];
  6'b011011:    qh <= q[27:26];
  6'b011001:    qh <= q[25:24];
  6'b010111:    qh <= q[23:22];
  6'b010101:    qh <= q[21:20];
  6'b010011:    qh <= q[19:18];
  6'b010001:    qh <= q[17:16];
  6'b001111:    qh <= q[15:14];
  6'b001101:    qh <= q[13:12];
  6'b001011:    qh <= q[11:10];
  6'b001001:    qh <= q[ 9:8];
  6'b000111:    qh <= q[ 7:6];
  6'b000101:    qh <= q[ 5:4];
  default:              qh <= q[ 7:6];
  endcase

endmodule