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// ============================================================================
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// ============================================================================
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// __
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// __
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// \\__/ o\ (C) 2015-2018 Robert Finch, Waterloo
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// \\__/ o\ (C) 2015-2019 Robert Finch, Waterloo
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// \ __ / All rights reserved.
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// \ __ / All rights reserved.
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// \/_// robfinch<remove>@finitron.ca
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// \/_// robfinch<remove>@finitron.ca
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// ||
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// ||
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//
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//
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//
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//
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//
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//
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// Compute the graphics address
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// Compute the graphics address
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//
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//
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module gfx_CalcAddress6(clk, base_address_i, color_depth_i, hdisplayed_i, x_coord_i, y_coord_i,
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module gfx_CalcAddress6(clk, base_address_i, color_depth_i, hdisplayed_i, x_coord_i, y_coord_i,
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address_o, mb_o, me_o, ce_o);
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address_o, mb_o, me_o, ce_o);
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parameter SW = 128; // strip width in bits
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parameter BN = SW==128 ? 6 : SW==64 ? 5 : 4;
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input clk;
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input clk;
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input [31:0] base_address_i;
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input [31:0] base_address_i;
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input [2:0] color_depth_i;
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input [2:0] color_depth_i;
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input [11:0] hdisplayed_i; // pixel per line
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input [11:0] hdisplayed_i; // pixel per line
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input [11:0] x_coord_i;
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input [11:0] x_coord_i;
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input [11:0] y_coord_i;
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input [11:0] y_coord_i;
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output [31:0] address_o;
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output [31:0] address_o;
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output [5:0] mb_o; // mask begin
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output [BN:0] mb_o; // mask begin
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output [5:0] me_o; // mask end
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output [BN:0] me_o; // mask end
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output [5:0] ce_o; // color bits end
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output [BN:0] ce_o; // color bits end
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parameter BPP4 = 3'd0;
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parameter BPP4 = 3'd0;
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parameter BPP8 = 3'd1;
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parameter BPP8 = 3'd1;
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parameter BPP12 = 3'd2;
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parameter BPP12 = 3'd2;
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parameter BPP16 = 3'd3;
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parameter BPP16 = 3'd3;
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// This coefficient is a fixed point fraction representing the inverse of the
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// This coefficient is a fixed point fraction representing the inverse of the
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// number of pixels per strip. The inverse (reciprocal) is used for a high
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// number of pixels per strip. The inverse (reciprocal) is used for a high
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// speed divide operation.
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// speed divide operation.
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reg [15:0] coeff;
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reg [15:0] coeff;
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always @(color_depth_i)
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always @(color_depth_i)
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case(SW)
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128:
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case(color_depth_i)
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BPP4: coeff = 2048; // 1/32 * 65536
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BPP8: coeff = 4096; // 1/16 * 65536
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BPP12: coeff = 6554; // 1/10 * 65536
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BPP16: coeff = 8192; // 1/8 * 65536
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BPP20: coeff = 10923; // 1/6 * 65536
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BPP32: coeff = 16384; // 1/4 * 65536
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default: coeff = 8192;
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endcase
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64:
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case(color_depth_i)
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case(color_depth_i)
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BPP4: coeff = 4096; // 1/16 * 65536
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BPP4: coeff = 4096; // 1/16 * 65536
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BPP8: coeff = 8192; // 1/8 * 65536
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BPP8: coeff = 8192; // 1/8 * 65536
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BPP12: coeff = 13107; // 1/5 * 65536
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BPP12: coeff = 13107; // 1/5 * 65536
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BPP16: coeff = 16384; // 1/4 * 65536
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BPP16: coeff = 16384; // 1/4 * 65536
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BPP20: coeff = 21845; // 1/3 * 65536
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BPP20: coeff = 21845; // 1/3 * 65536
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BPP32: coeff = 32768; // 1/2 * 65536
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BPP32: coeff = 32767; // 1/2 * 65536
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default: coeff = 16384;
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default: coeff = 16384;
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endcase
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endcase
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32:
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case(color_depth_i)
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BPP4: coeff = 8192; // 1/8 * 65536
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BPP8: coeff = 16384; // 1/4 * 65536
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BPP12: coeff = 32767; // 1/2 * 65536
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BPP16: coeff = 32767; // 1/2 * 65536
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BPP20: coeff = 65535; // 1/1 * 65536
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BPP32: coeff = 65535; // 1/1 * 65536
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default: coeff = 32767;
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endcase
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default: // 128
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case(color_depth_i)
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BPP4: coeff = 2048; // 1/32 * 65536
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BPP8: coeff = 4096; // 1/16 * 65536
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BPP12: coeff = 6554; // 1/10 * 65536
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BPP16: coeff = 8192; // 1/8 * 65536
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BPP20: coeff = 10923; // 1/6 * 65536
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BPP32: coeff = 16384; // 1/4 * 65536
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default: coeff = 8192;
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endcase
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endcase
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// Bits per pixel minus one.
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// Bits per pixel minus one.
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reg [5:0] bpp;
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reg [5:0] bpp;
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always @(color_depth_i)
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always @(color_depth_i)
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case(color_depth_i)
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case(color_depth_i)
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default: cbpp = 11;
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default: cbpp = 11;
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endcase
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endcase
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// This coefficient is the number of bits used by all pixels in the strip.
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// This coefficient is the number of bits used by all pixels in the strip.
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// Used to determine pixel placement in the strip.
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// Used to determine pixel placement in the strip.
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reg [6:0] coeff2;
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reg [7:0] coeff2;
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always @(color_depth_i)
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always @(color_depth_i)
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case(color_depth_i)
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case(color_depth_i)
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BPP4: coeff2 = 64;
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BPP4: coeff2 = SW;
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BPP8: coeff2 = 64;
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BPP8: coeff2 = SW;
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BPP12: coeff2 = 60;
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BPP12: coeff2 = SW==128 ? 120 : SW==64 ? 60 : 24;
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BPP16: coeff2 = 64;
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BPP16: coeff2 = SW;
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BPP20: coeff2 = 60;
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BPP20: coeff2 = SW==128 ? 120 : SW==64 ? 60 : 20;
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BPP32: coeff2 = 64;
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BPP32: coeff2 = SW;
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default: coeff2 = 64;
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default: coeff2 = SW;
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endcase
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endcase
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// Compute the fixed point horizonal strip number value. This has 16 binary
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// Compute the fixed point horizonal strip number value. This has 16 binary
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// point places.
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// point places.
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wire [27:0] strip_num65k = x_coord_i * coeff;
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wire [27:0] strip_num65k = x_coord_i * coeff;
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wire [13:0] strip_num = strip_num65k[27:16];
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wire [13:0] strip_num = strip_num65k[27:16];
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// Calculate pixel position within strip using the fractional part of the
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// Calculate pixel position within strip using the fractional part of the
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// horizontal strip number.
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// horizontal strip number.
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wire [15:0] strip_fract = strip_num65k[15:0]+16'h7F; // +7F to round
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wire [15:0] strip_fract = strip_num65k[15:0]+16'h7F; // +7F to round
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// Pixel beginning bit is ratio of pixel # into all bits used by pixels
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// Pixel beginning bit is ratio of pixel # into all bits used by pixels
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wire [14:0] ndx = strip_fract[15:7] * coeff2;
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wire [15:0] ndx = strip_fract[15:7] * coeff2;
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assign mb_o = ndx[12:7]; // Get whole pixel position (discard fraction)
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assign mb_o = ndx[15:9]; // Get whole pixel position (discard fraction)
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assign me_o = mb_o + bpp; // Set high order position for mask
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assign me_o = mb_o + bpp; // Set high order position for mask
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assign ce_o = mb_o + cbpp;
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assign ce_o = mb_o + cbpp;
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// num_strips is essentially a constant value unless the screen resolution changes.
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// num_strips is essentially a constant value unless the screen resolution changes.
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// Gain performance here by regstering the multiply so that there aren't two
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// Gain performance here by regstering the multiply so that there aren't two
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// cascaded multiplies when calculating the offset.
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// cascaded multiplies when calculating the offset.
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reg [27:0] num_strips65k;
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reg [27:0] num_strips65k;
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always @(posedge clk)
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always @(posedge clk)
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num_strips65k <= hdisplayed_i * coeff;
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num_strips65k <= hdisplayed_i * coeff;
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wire [11:0] num_strips = num_strips65k[27:16];
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wire [11:0] num_strips = num_strips65k[27:16];
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wire [31:0] offset = {(({4'b0,num_strips} * y_coord_i) + strip_num),3'h0};
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wire [31:0] offset = {(({4'b0,num_strips} * y_coord_i) + strip_num),SW==128 ? 4'h0 : SW==64 ? 3'h0 : 2'd0};
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assign address_o = base_address_i + offset;
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assign address_o = base_address_i + offset;
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endmodule
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endmodule
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